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GHSA-MH2Q-Q3FH-2475

Vulnerability from github – Published: 2026-04-07 20:12 – Updated: 2026-04-24 20:04
VLAI
Summary
OpenTelemetry-Go: multi-value `baggage` header extraction causes excessive allocations (remote dos amplification)
Details

multi-value baggage: header extraction parses each header field-value independently and aggregates members across values. this allows an attacker to amplify cpu and allocations by sending many baggage: header lines, even when each individual value is within the 8192-byte per-value parse limit.

severity

HIGH (availability / remote request amplification)

relevant links

  • repository: https://github.com/open-telemetry/opentelemetry-go
  • pinned callsite: https://github.com/open-telemetry/opentelemetry-go/blob/1ee4a4126dbdd1bc79e9fae072fa488beffac52a/propagation/baggage.go#L58

vulnerability details

pins: open-telemetry/opentelemetry-go@1ee4a4126dbdd1bc79e9fae072fa488beffac52a as-of: 2026-02-04 policy: direct (no program scope provided)

callsite: propagation/baggage.go:58 (extractMultiBaggage) attacker control: inbound HTTP request headers (many baggage field-values) → propagation.HeaderCarrier.Values("baggage") → repeated baggage.Parse + member aggregation

root cause

extractMultiBaggage iterates over all baggage header field-values and parses each one independently, then appends members into a shared slice. the 8192-byte parsing cap applies per header value, but the multi-value path repeats that work once per header line (bounded only by the server/proxy header byte limit).

impact

in a default net/http configuration (max header bytes 1mb), a single request with many baggage: header field-values can cause large per-request allocations and increased latency.

example from the attached PoC harness (darwin/arm64; 80 values; 40 requests):

  • canonical: per_req_alloc_bytes=10315458 and p95_ms=7
  • control: per_req_alloc_bytes=133429 and p95_ms=0

proof of concept

canonical:

mkdir -p poc
unzip poc.zip -d poc
cd poc
make test

output (excerpt):

[CALLSITE_HIT]: propagation/baggage.go:58 extractMultiBaggage
[PROOF_MARKER]: baggage_multi_value_amplification p95_ms=7 per_req_alloc_bytes=10315458 per_req_allocs=16165

control:

cd poc
make control

control output (excerpt):

[NC_MARKER]: baggage_single_value_baseline p95_ms=0 per_req_alloc_bytes=133429 per_req_allocs=480

expected: multiple baggage header field-values should be semantically equivalent to a single comma-joined baggage value and should not multiply parsing/alloc work within the effective header byte budget. actual: multiple baggage header field-values trigger repeated parsing and member aggregation, causing high per-request allocations and increased latency even when each individual value is within 8192 bytes.

fix recommendation

avoid repeated parsing across multi-values by enforcing a global budget and/or normalizing multi-values into a single value before parsing. one mitigation approach is to treat multi-values as a single comma-joined string and cap total parsed bytes (for example 8192 bytes total).

fix accepted when: under the default PoC harness settings, canonical stays within 2x of control for per_req_alloc_bytes and per_req_allocs, and p95_ms stays below 2ms.

poc.zip PR_DESCRIPTION.md

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= 1.40.0"
      },
      "package": {
        "ecosystem": "Go",
        "name": "go.opentelemetry.io/otel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.36.0"
            },
            {
              "fixed": "1.41.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-29181"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400",
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-07T20:12:57Z",
    "nvd_published_at": "2026-04-07T21:17:16Z",
    "severity": "HIGH"
  },
  "details": "multi-value `baggage:` header extraction parses each header field-value independently and aggregates members across values. this allows an attacker to amplify cpu and allocations by sending many `baggage:` header lines, even when each individual value is within the 8192-byte per-value parse limit.\n\n## severity\n\nHIGH (availability / remote request amplification)\n\n## relevant links\n\n- repository: https://github.com/open-telemetry/opentelemetry-go\n- pinned callsite: https://github.com/open-telemetry/opentelemetry-go/blob/1ee4a4126dbdd1bc79e9fae072fa488beffac52a/propagation/baggage.go#L58\n\n## vulnerability details\n\n**pins:** open-telemetry/opentelemetry-go@1ee4a4126dbdd1bc79e9fae072fa488beffac52a\n**as-of:** 2026-02-04\n**policy:** direct (no program scope provided)\n\n**callsite:** propagation/baggage.go:58 (`extractMultiBaggage`)\n**attacker control:** inbound HTTP request headers (many `baggage` field-values) \u2192 `propagation.HeaderCarrier.Values(\"baggage\")` \u2192 repeated `baggage.Parse` + member aggregation\n\n### root cause\n\n`extractMultiBaggage` iterates over all `baggage` header field-values and parses each one independently, then appends members into a shared slice. the 8192-byte parsing cap applies per header value, but the multi-value path repeats that work once per header line (bounded only by the server/proxy header byte limit).\n\n### impact\n\nin a default `net/http` configuration (max header bytes 1mb), a single request with many `baggage:` header field-values can cause large per-request allocations and increased latency.\n\nexample from the attached PoC harness (darwin/arm64; 80 values; 40 requests):\n\n- canonical: `per_req_alloc_bytes=10315458` and `p95_ms=7`\n- control: `per_req_alloc_bytes=133429` and `p95_ms=0`\n\n## proof of concept\n\ncanonical:\n\n```bash\nmkdir -p poc\nunzip poc.zip -d poc\ncd poc\nmake test\n```\n\noutput (excerpt):\n\n```\n[CALLSITE_HIT]: propagation/baggage.go:58 extractMultiBaggage\n[PROOF_MARKER]: baggage_multi_value_amplification p95_ms=7 per_req_alloc_bytes=10315458 per_req_allocs=16165\n```\n\ncontrol:\n\n```bash\ncd poc\nmake control\n```\n\ncontrol output (excerpt):\n\n```\n[NC_MARKER]: baggage_single_value_baseline p95_ms=0 per_req_alloc_bytes=133429 per_req_allocs=480\n```\n\n**expected:** multiple `baggage` header field-values should be semantically equivalent to a single comma-joined `baggage` value and should not multiply parsing/alloc work within the effective header byte budget.\n**actual:** multiple `baggage` header field-values trigger repeated parsing and member aggregation, causing high per-request allocations and increased latency even when each individual value is within 8192 bytes.\n\n## fix recommendation\n\navoid repeated parsing across multi-values by enforcing a global budget and/or normalizing multi-values into a single value before parsing. one mitigation approach is to treat multi-values as a single comma-joined string and cap total parsed bytes (for example 8192 bytes total).\n\n**fix accepted when:** under the default PoC harness settings, canonical stays within 2x of control for `per_req_alloc_bytes` and `per_req_allocs`, and `p95_ms` stays below 2ms.\n\n\n[poc.zip](https://github.com/user-attachments/files/25079945/poc.zip)\n[PR_DESCRIPTION.md](https://github.com/user-attachments/files/25079946/PR_DESCRIPTION.md)",
  "id": "GHSA-mh2q-q3fh-2475",
  "modified": "2026-04-24T20:04:24Z",
  "published": "2026-04-07T20:12:57Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/open-telemetry/opentelemetry-go/security/advisories/GHSA-mh2q-q3fh-2475"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-29181"
    },
    {
      "type": "WEB",
      "url": "https://github.com/open-telemetry/opentelemetry-go/pull/7880"
    },
    {
      "type": "WEB",
      "url": "https://github.com/open-telemetry/opentelemetry-go/commit/aa1894e09e3fe66860c7885cb40f98901b35277f"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/open-telemetry/opentelemetry-go"
    },
    {
      "type": "WEB",
      "url": "https://github.com/open-telemetry/opentelemetry-go/releases/tag/v1.41.0"
    }
  ],
  "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": "OpenTelemetry-Go: multi-value `baggage` header extraction causes excessive allocations (remote dos amplification)"
}



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