Apache Tomcat is widely deployed; this HTTP/2 race condition can enable cross-request trailer injection leading to request smuggling, header pollution and possible RCE, requiring org-wide patching.
CVE-2026-77762
Race condition in Apache Tomcat HTTP/2 allows trailer injection across requests.
do firstUpgrade to a fixed release: <= 7.0.109.
Is CVE-2026-77762 being exploited?
Not confirmed. CVE-2026-77762 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 0.46% probability of exploitation in the next 30 days.
How severe is CVE-2026-77762?
CVE-2026-77762 is rated High with a CVSS score of 8.1. 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-2026-77762?
Yes. A fix has been recorded for CVE-2026-77762. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-77762 affect?
CVE-2026-77762 affects Apache Tomcat 11.0.0-M1 - 11.0.25, Apache Tomcat 10.1.0-M1 - 10.1.59, Apache Tomcat 9.0.39 - 9.0.121, Apache Tomcat 8.5.59 - 8.5.100 (EOL). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-77762?
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 race condition lets attacker inject trailer fields into other requests, enabling request smuggling, header/trailer pollution, auth bypass and potential RCE.
Immediate action required
- affected>= 11.0.0-M1 and <= 11.0.25
- affected>= 10.1.0-M1 and <= 10.1.59
- affected>= 9.0.39 and <= 9.0.121
- affected>= 8.56.59 and <= 8.5.100
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.
cisa ssvc
- exploitation
- none
- automatable
- no
- 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
- 24 Sept 2026Analysed by vulneraibility.com · 1 day later
- 30 Sept 2026CVE record last updated · 6 days later
- Advisorylists.apache.org /thread/y5r9fvjo7ol24mkoyoc0st8bqrfyqcyn
- Linkopenwall.com /lists/oss-security/2026/09/23/23
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
- Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.