What is the CVSS score of CVE-2026-58066?

CVE-2026-58066 has a CVSS 3.0 base score of 9.8 (Critical). CVSS vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.2%.

Which versions of Rocket.Chat are affected by CVE-2026-58066?

Rocket.Chat versions prior to 8.7.0 contain a critical SAML authentication bypass that allows unauthenticated attackers to gain administrative access by manipulating XML signatures.. A patch is available.

How to fix or mitigate CVE-2026-58066?

Within 24 hours, inventory all Rocket.Chat instances and identify those running versions before 8.7.0 with SAML enabled; prioritize production environments for immediate isolation if exploitation is suspected. Within 7 days, deploy patches to all affected systems: upgrade to version 8.7.0 or apply branch-specific fixes (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 for older installations). Within 30 days, conduct post-deployment validation of SAML authentication workflows, audit user access logs from the exposure window for anomalous logins, and establish monitoring for signature validation failures.

Rocket.Chat CVE-2026-58066

EUVD-2026-51023 CRITICAL

Improper Authentication (CWE-287)

2026-07-30 hackerone

GHSA-f3wj-pr2w-q3fm

Authentication Bypass Rocket Chat

9.8

CVSS 3.0 · Vendor: hackerone

Severity by source

Vendor (hackerone) PRIMARY

9.8 CRITICAL

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

vuln.today AI

9.8 CRITICAL

Network-facing SAML endpoint, no auth or interaction needed once a signed sample is held, yielding full impersonation of any account including admin - total C/I/A impact.

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

4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (hackerone).

CVSS VectorVendor: hackerone

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Source Code Evidence Fetched

Jul 30, 2026 - 08:29 vuln.today

Analysis Generated

Jul 30, 2026 - 08:29 vuln.today

Patch available

Jul 30, 2026 - 07:03 EUVD

CVE Published

Jul 30, 2026 - 06:03 cve.org

CRITICAL 9.8

DescriptionCVE.org

Rocket.Chat's SAML SSO before versions 8.7.0, 8.6.1, 8.5.2, 8.4.5, 8.3.7, 8.2.7, 8.1.7, 8.0.8, and 7.10.14 verified XML signatures but did not bind the validated signature to samlp:Response / saml:Assertion. An attacker could submit a wrapped document carrying forged identity attributes alongside any valid signature made by the trusted IdP certificate, and log in as an arbitrary user.

AnalysisAI

Authentication bypass in Rocket.Chat's SAML SSO before 8.7.0 (and the 8.6.1, 8.5.2, 8.4.5, 8.3.7, 8.2.7, 8.1.7, 8.0.8, 7.10.14 branch fixes) lets a remote unauthenticated attacker log in as any user, including administrators, via an XML Signature Wrapping attack. The parser validated that a signature was cryptographically correct against the trusted IdP certificate but never bound that signature to the samlp:Response/saml:Assertion actually processed, so forged identity attributes wrapped alongside a genuine signature were accepted. There is no public exploit identified at time of analysis, but a HackerOne report and an upstream patch with signature-scope regression tests exist; EPSS/KEV data was not provided.

Technical ContextAI

The flaw lives in Rocket.Chat's Meteor SAML accounts module (apps/meteor/app/meteor-accounts-saml/server/lib/parsers/Response.ts), which parses SAML 2.0 assertions using the xml-crypto library. The root cause is CWE-287 (Improper Authentication) manifesting specifically as XML Signature Wrapping (XSW): xml-crypto confirmed the signature was mathematically valid over *some* referenced element, but the application never checked that the signed ds:Reference URI matched the ID of the Response/Assertion whose attributes it then trusted. An attacker can therefore relocate a legitimately signed element and inject an unsigned sibling containing arbitrary NameID/attribute values. The patch adds getElementId() and signatureCoversElement() to require that every signature reference URI equals the ID of the processed element, and additionally enforces that the SAML Response is the document root ('response !== doc.documentElement' rejection) to block wrapper-envelope tricks.

RemediationAI

Vendor-released patch: upgrade to the fixed release on your 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 (whichever is the next patched version at or above your current line), as delivered in the security hotfix of Rocket.Chat PR #41233 (https://github.com/RocketChat/Rocket.Chat/pull/41233); see also https://docs.rocket.chat/docs/security-fixes-and-updates. If you cannot patch immediately, the most effective compensating control is to disable SAML SSO in Admin > Settings > SAML and fall back to another authentication method (password/OAuth/LDAP), which fully closes the vector at the cost of removing SAML login for users. Where SAML must remain enabled, restrict network access to the SAML validation endpoints (e.g., /_saml/validate) to trusted IdP source ranges via a reverse proxy or firewall and monitor authentication logs for logins that do not correlate with expected IdP sessions - note this reduces but does not eliminate risk since the attacker only needs one valid signed assertion. Prioritize patching over workarounds.