Affects Apache Tomcat, a widely deployed Java web server; regression enables HTTP/2 request smuggling with a high CVSS score and broad impact.
CVE-2026-86350
HTTP/2 request-smuggling regression in Apache Tomcat causes header mix-ups.
Is CVE-2026-86350 being exploited?
Not confirmed. CVE-2026-86350 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 0.48% probability of exploitation in the next 30 days.
How severe is CVE-2026-86350?
CVE-2026-86350 is rated Critical with a CVSS score of 9.1. 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-2026-86350?
Yes. A fix has been recorded for CVE-2026-86350. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-86350 affect?
CVE-2026-86350 affects Apache Tomcat 11.0.22 - 11.0.25, Apache Tomcat 10.1.55 - 10.1.59, Apache Tomcat 9.0.118 - 9.0.121, Fixed in 11.0.26, 10.1.60, 9.0.122. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-86350?
Upgrade to 11.0.26, 10.1.60 or 9.0.122 immediately.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
HTTP/2 request/response smuggling causing header mix-up; can enable request hijack, cache poisoning, auth bypass, data leakage, and session takeover.
Immediate action required
- affected>= 11.0.22 and <= 11.0.25
- affected>= 10.1.55 and <= 10.1.59
- affected>= 9.0.118 and <= 9.0.121
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.
public exploits
Unvetted proof-of-concept code on GitHub: 1 GitHub proof of concept
- abraxas/CVE-2026-86350 · 1 ★
Listed so you can judge urgency, not as a recommendation to run anything. GitHub “proofs of concept” are unvetted: some are fake or carry malware. Exploit-DB marks the entries its staff verified.
cisa ssvc
- exploitation
- none
- automatable
- yes
- technical impact
- total
Assessed by CISA 23 Sept 2026 (SSVC 2.0.3).
timeline
- 23 Sept 2026Published
- 23 Sept 2026CISA SSVC assessment: exploitation none · same day later
- 23 Sept 2026CVE record last updated · same day later
- 24 Sept 2026Analysed by vulneraibility.com · 1 day later
- 25 Sept 2026First proof-of-concept repository on GitHub (unvetted) · 1 day later
- Advisorylists.apache.org /thread/mss45z99lcdd5dtpgcn45dy82f3toswc
sources
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- PoC-in-GitHub: GitHub repositories that claim a proof of concept
- Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.