CVE-2025-31699 Apache Software Foundation CVE debrief

Who should care

Defenders of Apache Traffic Server deployments should assess exposure and prioritize upgrading to fixed versions to prevent potential request smuggling attacks, which could disrupt user requests, poison the cache, or bypass access controls. This includes operators, platform administrators, vulnerability management teams, and security teams responsible for ensuring the security and integrity of Apache Traffic Server deployments.

Why it matters

Defenders of Apache Traffic Server should prioritize upgrading to fixed versions to prevent potential request smuggling attacks, which could disrupt user requests, poison the cache, or bypass access controls. Evidence is based on official CVE and source item records.

• Potential disruption of user requests
• Possible poisoning of the cache
• Bypass of access controls through request smuggling

Technical summary

Apache Traffic Server can return an origin connection to the shared pool while the origin is still waiting on a request body the client declared but never fully sent, including when the client used Expect: 100-continue. The origin then reads a later request on that connection as leftover body data, which lets an attacker smuggle requests past ATS access controls, disrupt other users' requests, or poison the cache.

Defensive priority

Upgrade to fixed versions

Recommended defensive actions

• Upgrade Apache Traffic Server to version 9.2.16, 10.1.5, or 10.2.1
• Review and update affected versions
• Monitor for potential request smuggling attacks
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance.
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed.
• Review compensating controls for exposed systems while remediation is scheduled and verified.

Evidence notes

The CVE record and source item provide details on the vulnerability in Apache Traffic Server, including affected versions and recommended upgrades. Evidence is based on official CVE and source item records, which indicate that Apache Traffic Server can return an origin connection to the shared pool while the origin is still waiting on a request body the client declared but never fully sent. This issue affects Apache Traffic Server: from 8.0.0 through 8.1.11, from 9.0.0 through 9.2.15, from 10.0.0 through 10.1.4, 10.2.0. Users are also

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.