Apache Tomcat: TOCTOU race condition in APR/Native connector Unix domain sockets
Summary
A time-of-check time-of-use race condition in the APR/Native connector of Apache Tomcat 9 allows a local, unprivileged user to access a Unix domain socket created by Tomcat. The fix for CVE-2026-65183 covered only the NIO connector, so the APR/Native connector remained affected. Exploitation requires a local account on the host and the APR/Native connector with Unix domain sockets configured; Apache rates the issue Low.
Affected
- Apache Tomcat 9.0.47 through 9.0.122 (Apache advisory)
- Discrepancy: Apache Tomcat 9 security page gives 9.0.92 to 9.0.122; treat 9.0.47 to 9.0.91 as potentially affected until Apache clarifies
- Tomcat 10.1 and 11.0: not confirmed by Apache for this CVE
- Unknown whether distribution packages (e.g. Ubuntu tomcat9) are affected
Fixed in
- Apache Tomcat 9.0.123 (released 12 Oct 2026, fixed with commit 894158fd)
Workaround
- No workaround confirmed by Apache; upgrade is the only listed fix
- Interim measure if patching is not possible: restrict the socket's parent directory to the Tomcat service account (mode 0700), not confirmed by Apache for this CVE
- Consider disabling Unix domain socket use in the connector if not required
Exploitation
- CISA SSVC: Exploitation none, Automatable no, Technical Impact total
- Not listed in CISA KEV (per Strix)
- No public proof-of-concept or confirmed exploitation found as of 1 Nov 2026 (limited search)
Our recommendation
- Check whether the APR/Native connector with Unix domain sockets is used (Tomcat Native installed, socket configured)
- Upgrade Apache Tomcat 9 to 9.0.123 in the next regular maintenance window; patch sooner on multi-tenant or shared hosts with untrusted local users
- Until patched, restrict the socket directory to the Tomcat service account
- Verify the CVSS score against NVD, which was still awaiting analysis; the vector lists network access while the flaw is local
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Apache mailing list advisory lists.apache.org
- Apache Tomcat 9 security page tomcat.apache.org
- Apache Tomcat 9.0.123 release catalog release-catalog.apache.org
- Tomcat 9.0 changelog tomcat.apache.org
- Ubuntu security tracker ubuntu.com
- Strix CVE entry www.strix.ai
- VulDB entry vuldb.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 18:41.
Original description (NVD)
Time-of-check time-of-use (TOCTOU) race condition vulnerability in Apache Tomcat when creating unix domain sockets for the APR/Native connector allows an unauthorised local user to access the unix domain socket. The fix for CVE-2026-65183 only addressed the NIO connector. It did not address the same issue in the APR/Native connector. This issue affects Apache Tomcat: from 9.0.47 through 9.0.122. Users are recommended to upgrade to version 9.0.123, which fixes the issue.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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