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CVE-2026-58066 – Authentication Bypass – Rocket.Chat SAML SSO before 8.7.0

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Summary

CVE-2026-58066 is a critical SAML XML Signature Wrapping (XSW) authentication bypass vulnerability in Rocket.Chat’s SSO implementation, affecting all versions before 8.7.0 and multiple prior stable branches. With a CVSS score of 9.8 (Critical), an unauthenticated remote attacker can craft a malicious SAML document to forge identity attributes and authenticate as any arbitrary user — including administrators — without valid credentials. Rocket.Chat has released patched versions across all affected branches.

Technical details

  • Root cause: Rocket.Chat’s SAML service provider verified that an inbound XML signature was cryptographically valid against the trusted Identity Provider (IdP) certificate, but never bound that validated signature to the specific samlp:Response or saml:Assertion element being processed (CWE-287: Improper Authentication). This decoupling is the defining flaw of XML Signature Wrapping (XSW) attacks.
  • Trigger conditions: SAML SSO must be configured on the Rocket.Chat instance. SAML/SSO integration is a common enterprise deployment pattern for Rocket.Chat.
  • Attack vector: A remote, unauthenticated attacker submits a specially crafted SAML document that wraps forged identity attributes alongside a legitimately signed XML node obtained from the trusted IdP. Because signature validation succeeds against the legitimate node, the Rocket.Chat service provider accepts the forged assertion and issues a session for the targeted account.
  • Impact: Complete authentication bypass — the attacker can log in as any user, including workspace administrators — resulting in full compromise of confidentiality, integrity, and availability of the affected Rocket.Chat instance. Per CISA’s SSVC assessment, the vulnerability is automatable with total technical impact.

Affected software

  • Rocket.Chat versions before 8.7.0 (latest stable branch)
  • Rocket.Chat versions before 8.6.1 (8.6.x stable branch)
  • Rocket.Chat versions before 8.5.2 (8.5.x stable branch)
  • Rocket.Chat versions before 8.4.5 (8.4.x stable branch)
  • Rocket.Chat versions before 8.3.7 (8.3.x stable branch)
  • Rocket.Chat versions before 8.2.7 (8.2.x stable branch)
  • Rocket.Chat versions before 8.1.7 (8.1.x stable branch)
  • Rocket.Chat versions before 8.0.8 (8.0.x stable branch)
  • Rocket.Chat versions before 7.10.14 (7.10.x stable branch)

Severity

CVSS v3.0 base score: 9.8 (Critical)
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate — patch: Upgrade to one of the fixed releases corresponding to your deployment branch: 8.7.0, 8.6.1, 8.5.2, 8.4.5, 8.3.7, 8.2.7, 8.1.7, 8.0.8, or 7.10.14. The upstream fix was backported across all active stable branches (see GitHub PR #41233).
  • If immediate patching is not feasible: Temporarily disable SAML SSO in Rocket.Chat’s Administration → SSO settings until the patch can be applied. This removes the attack surface entirely, as the vulnerability is only exploitable when SAML SSO is active.
  • Detection: Review authentication logs for anomalous SAML-based login events — particularly logins attributed to administrator accounts originating from unexpected sources or at unusual times.

IONIX Status

The IONIX research team is tracking ongoing exploitation attempts and recommends immediate patching. Potentially affected assets are outlined in this post.

References

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