Security Digest · Vulnerability record
CVE-2026-68763: Apache Tomcat: DoS via allocation leak in HTTP/2 backlog tracking when a stream is reset
Uncontrolled Resource Consumption vulnerability in Apache Tomcat via an allocation leak in the HTTP/2 backlog tracking when a stream is reset This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.24, from 10.1.0-M1 through 10.1.57, from 9.0.39 through 9.0.120.
CVSS 7.5 High EPSS 0.7% · p54 Patch this week
Should you act?
Normal patch cycle
No exploitation signal; fix it in your next routine update if you are affected. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.7%, percentile 54: FIRST’s model estimates a 0.7% chance of exploitation activity in the next 30 days, higher than 54% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Editorial verdict: Patch this week. Apache Tomcat August 2026: Security Constraint Bypasses — Upgrade Tomcat, including the copy embedded in Spring Boot apps, this week; the access-control bypasses matter wherever you rely on web.xml security constraints or container authentication, and none is known to be exploited.
What it is
Uncontrolled Resource Consumption vulnerability in Apache Tomcat via an allocation leak in the HTTP/2 backlog tracking when a stream is reset This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.24, from 10.1.0-M1 through 10.1.57, from 9.0.39 through 9.0.120. The following versions were EOL at the time the CVE was created but are known to be affected: from 8.5.59 through 8.5.100. Other unsupported versions may also be affected. Users are recommended to upgrade to version 11.0.25, 10.1.58 or 9.0.121, which fix the issue.
Weakness type: CWE-400.
Product: Apache Software Foundation Apache Tomcat · Assigned by: apache · Published: 2026-08-25
Affected and fixed versions
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| Apache Software Foundation | Apache Tomcat | 11.0.0-M1 <= 11.0.24, 10.1.0-M1 <= 10.1.57, 9.0.39 <= 9.0.120, 8.5.59 <= 8.5.100 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| CISA-ADP | 3.1 | 7.5 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: none (no login)
- User interaction: none
- Scope: unchanged
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none, automatable yes, technical impact partial.
- FIRST EPSS (model of 2026-10-21): 0.74% probability of exploitation activity in the next 30 days; percentile 54.
Timeline
- — CVE record published by apache
- — erroneo.us brief: Apache Tomcat August 2026: Security Constraint Bypasses
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vendor and project advisories, patches
- lists.apache.org lists.apache.org
Vulnerability records
- CVE.org record CVE-2026-68763 cve.org
- NVD entry CVE-2026-68763 nvd.nist.gov
Other references from the CVE record and advisory
- openwall.com openwall.com