Critical flaw in a widely used proxy (Apache Traffic Server) enabling request smuggling, cache poisoning and bypasses across many versions; requires org-wide remediation.
CVE-2026-58155
Apache Traffic Server header truncation enables request smuggling and policy bypass.
Is CVE-2026-58155 being exploited?
Not confirmed. CVE-2026-58155 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.40% probability of exploitation in the next 30 days.
How severe is CVE-2026-58155?
CVE-2026-58155 is rated Critical with a CVSS score of 9.2. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-58155?
Yes. A fix has been recorded for CVE-2026-58155. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-58155 affect?
CVE-2026-58155 affects Apache Traffic Server 8.0.0 - 8.1.9, Apache Traffic Server 9.0.0 - 9.2.14, Apache Traffic Server 10.0.0 - 10.1.3. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-58155?
Upgrade to ATS 9.2.15 or 10.1.4 immediately; if unpatchable, restrict/limit ATS and monitor logs.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote attackers can smuggle requests, cause header aliasing, cache poisoning and bypass access controls.
Immediate action required
- affected>= 8.0.0 and <= 8.1.9
- affected>= 9.0.0 and <= 9.2.14
- affected>= 10.0.0 and <= 10.1.3
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.