Unrated

Authentication Bypass in Apache Tomcat JNDIRealm GSSAPI Bind Authentication

IdentifiersCVE-2026-55957CWE-303

CVE-2026-55957 is an authentication bypass vulnerability in Apache Tomcat affecting deployments where JNDIRealm is configured to authenticate binds using GSSAPI. Apache describes the issue as a missing critical step in authentication. Under this specific configuration, Tomcat may accept authentication without the attacker providing the correct password. Affected versions are Tomcat 11.0.0-M1 through 11.0.4, 10.1.0-M1 through 10.1.36, 9.0.0.M1 through 9.0.100, 8.5.0 through 8.5.100, and 7.0.0 through 7.0.109.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows an attacker to bypass normal password verification and authenticate as a valid user in affected Tomcat deployments using the vulnerable JNDIRealm GSSAPI bind configuration. This can result in unauthorized access to applications and resources protected by Tomcat-managed authentication, potentially exposing sensitive data and enabling actions with the privileges of the impersonated or authenticated account.

Mitigation

If you can’t patch tonight, do this now.

If immediate patching is not possible, avoid using JNDIRealm configured to authenticate binds via GSSAPI in exposed or sensitive environments. Where feasible, switch to an alternative authentication configuration not affected by this flaw, restrict access to applications relying on the vulnerable realm, and closely monitor authentication logs for anomalous successful logins. These are temporary risk-reduction measures and do not replace upgrading to a fixed version.

Remediation

Patch, then assume compromise.

Upgrade Apache Tomcat to a fixed release. Apache recommends upgrading to 11.0.5, 10.1.37, or 9.0.101, depending on the branch in use. For older affected branches, move to a supported fixed version as soon as operationally possible. Validate after upgrade that JNDIRealm authentication using GSSAPI behaves as expected and that password verification is correctly enforced.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

ACTIVITY FEED

Recent activity

9 sources tracked across advisories and community write-ups. News coverage will land here when it surfaces.

9 SOURCESView more in app

No news coverage yet. Advisories and community discussion only.

What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.

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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity9

Community discussion across Reddit, Mastodon, and other social sources.

EXTERNAL REFERENCES

MITRE CVE

cve.org · CVE-2026-55957

NVD

nvd.nist.gov/vuln/detail/CVE-2026-55957

MITRE CWE · CWE-303

cwe.mitre.org