CVE-2026-43512: Apache Tomcat - Digest authenticator will authenticate any unknown user

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 1.3%, percentile 71: FIRST’s model estimates a 1.3% chance of exploitation activity in the next 30 days, higher than 71% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes org.apache.tomcat.embed:tomcat-embed-core (Maven) < 9.0.118, fixed in 9.0.118; org.apache.tomcat.embed:tomcat-embed-core (Maven) >= 10.1.0-M1, < 10.1.55, fixed in 10.1.55; org.apache.tomcat.embed:tomcat-embed-core (Maven) >= 11.0.0-M1, < 11.0.22, fixed in 11.0.22; org.apache.tomcat:tomcat (Maven) < 9.0.118, fixed in 9.0.118. Check your lockfile, including transitive dependencies.

What it is

DEPRECATED: Authentication Bypass Issues vulnerability in digest authentication in Apache Tomcat. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.21, from 10.1.0-M1 through 10.1.54, from 9.0.0.M1 through 9.0.117, from 8.5.0 through 8.5.100, from before 7.0.0. Older unsupported versions any also be affect Users are recommended to upgrade to version 11.0.22, 10.1.55 or 9.0.118 which fix the issue.

From the GitHub advisory

Versions Affected: Apache Tomcat 11.0.0-M1 to 11.0.21 Apache Tomcat 10.1.0-M1 to 10.1.54 Apache Tomcat 9.0.0.M1 to 9.0.117 Older, unsupported versions may also be affected

Description: When DIGEST authentication was configured, any user not known to the configured Realm would be authenticated if they presented the password "null".

Mitigation: Users of the affected versions should apply one of the following mitigations: - Upgrade to Apache Tomcat 11.0.22 or later - Upgrade to Apache Tomcat 10.1.55 or later - Upgrade to Apache Tomcat 9.0.118 or later

Weakness type: CWE-592, CWE-287.

Product: org.apache.tomcat.embed:tomcat-embed-core (Maven) · Assigned by: apache · Published: 2026-05-12

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 1.33% probability of exploitation activity in the next 30 days; percentile 71.

Timeline

• 2026-05-12 — CVE record published by apache
• 2026-05-12 — GitHub-reviewed advisory GHSA-h6fc-48rj-7qqh published (critical)
• 2026-05-14 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

1. lists.apache.org lists.apache.org

Vulnerability records

1. GitHub Advisory GHSA-h6fc-48rj-7qqh github.com
2. CVE.org record CVE-2026-43512 cve.org
3. NVD entry CVE-2026-43512 nvd.nist.gov

Other references from the CVE record and advisory

1. openwall.com openwall.com
2. github.com github.com
3. github.com github.com
4. github.com github.com
5. tomcat.apache.org tomcat.apache.org
6. tomcat.apache.org tomcat.apache.org
7. tomcat.apache.org tomcat.apache.org

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