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CVE-2026-55663 medium CVSS 5.6

Vulnerability in mediasoup (CVE-2026-55663)

Summary

Vulnerability in mediasoup (CVE-2026-55663). Risk of unauthorized operations or information disclosure. Exploitable via localVerificationTag. Mitigation: upgrade to 3.20.6 or later.

Original description

The description as published by the source.

Summary

mediasoup's built-in SCTP stack (introduced in v3.20.0) authenticates SCTP state cookies using only hardcoded magic byte sequences rather than a per-instance HMAC keyed with a secret, violating RFC 9260 Section 5.1.3. An on-path attacker targeting a PlainTransport with SCTP enabled (and no SRTP/DTLS protection) can craft a forged COOKIE-ECHO chunk that passes all validation, establishing an unauthorized SCTP association and gaining the ability to inject DataChannel messages as a trusted peer.

Details

RFC 9260 Section 5.1.3 states: "An endpoint MUST use a one-time-use secret key to protect the State Cookie." The mediasoup implementation ignores this requirement. The state cookie is defined in worker/include/RTC/SCTP/association/StateCookie.hpp with the following structure (44 bytes total):

  • Offset 0: Magic1 = "msworker" (hardcoded, 8 bytes)
  • Offset 8: localVerificationTag (4 bytes, attacker-controlled)
  • Offset 12: remoteVerificationTag (4 bytes, attacker-controlled)
  • Offset 16-27: TSN and window fields (attacker-controlled)
  • Offset 28: tieTag (8 bytes, attacker-controlled)
  • Offset 36: NegotiatedCapabilitiesField containing Magic2 = 0xAD81 (hardcoded)

The validation function StateCookie::IsMediasoupStateCookie() in worker/src/RTC/SCTP/association/StateCookie.cpp only checks:

  1. bufferLength == 44
  2. bytes[0:8] == "msworker" (Magic1, always the same)
  3. ntohs(bytes[38:40]) == 0xAD81 (Magic2, always the same)

No HMAC, no per-session sec…

Source: GitHub Security Advisories (Global) NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-55663 has been found in mediasoup.
Attackers can target a specific entry point like localVerificationTag over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.6/10.
What to do: upgrade mediasoup to 3.20.6 or later.
If unsure, ask your IT team or search "mediasoup CVE-2026-55663" on the vendor's site.

CVE-2026-55663 (mediasoup) — CWE-345 / CVSS v3 5.6
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: localVerificationTag / PlainTransport / srtpCryptoSuite / WebRtcTransport
Patched: 3.20.6 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-345) exists in mediasoup. Attackers reach the vulnerable code path via localVerificationTag without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of mediasoup. Attack surface: localVerificationTag / PlainTransport / srtpCryptoSuite / WebRtcTransport.

🔥 Severity

Severity: Medium (CVSS 5.6/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 3.20.6.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'mediasoup' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'mediasoup' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で mediasoup を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade mediasoup to 3.20.6

    ステージング環境で 3.20.6 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

npm mediasoup
[{"type":"SEMVER","events":[{"introduced":"3.20.0"},{"fixed":"3.20.6"}]}]
rust mediasoup
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.22.5"}]}]
crates.io mediasoup
[{"type":"SEMVER","events":[{"introduced":"0.22.0"},{"fixed":"0.22.5"}]}]

References

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