Apache Tomcat: HTTP/2 DoS via malformed request
Incomplete cleanup vulnerability in Apache Tomcat allows a malformed request to potentially (depends on timing) cause one request from another user to fail. This issue affects Apache Tomcat: from 11.0.19 through 11.0.25, from 10.1.53 through 10.1.59, from 9.0.116 through 9.0.121. Users are recommended to upgrade to version 11.0.26, 10.1.60 or 9.0.122, which fix the issue.
- Published
- Sep 23, 2026
- Updated
- Sep 23, 2026
- EPSS
- 0.3% · 16th percentile
- CWE
- CWE-459
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Report tools
Action score
29
Monitor
Low priority for now.
- CVSS
- 29 / 40 · 7.3 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.3%
CISA SSVC decision
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
Affected systems
—
Versions reported by the vendor
Affected version ranges reported by the assigning authority (apache). Independent of NVD's CPE analysis and usually ahead of it.
Apache Software Foundation Apache Tomcat
- 11.0.19 and later · up to and including 11.0.25affected · semver
- 10.1.53 and later · up to and including 10.1.59affected · semver
- 9.0.116 and later · up to and including 9.0.121affected · semver
- up to and including 8.5.100not affected · semver
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | tomcat10 | all versions | — |
| Debian:12 | tomcat9 | before 9.0.70-2 | 9.0.70-2 |
| Debian:13 | tomcat11 | all versions | — |
| Debian:14 | tomcat10 | before 10.1.60-1 | 10.1.60-1 |
| openSUSE:Tumbleweed | tomcat | before 9.0.122-1.1 | 9.0.122-1.1 |
| openSUSE:Tumbleweed | tomcat10 | before 10.1.60-1.1 | 10.1.60-1.1 |
| openSUSE:Tumbleweed | tomcat11 | before 11.0.26-1.1 | 11.0.26-1.1 |
| Red Hat:hummingbird:1 | tomcat10 | before 0:10.1.60-0.1.hum1 | 0:10.1.60-0.1.hum1 |
| Red Hat:hummingbird:1 | tomcat10-admin-webapps | before 0:10.1.60-0.1.hum1 | 0:10.1.60-0.1.hum1 |
| Red Hat:hummingbird:1 | tomcat10-common | before 0:10.1.60-0.1.hum1 | 0:10.1.60-0.1.hum1 |
| Red Hat:hummingbird:1 | tomcat10-docs-webapp | before 0:10.1.60-0.1.hum1 | 0:10.1.60-0.1.hum1 |
| Red Hat:hummingbird:1 | tomcat10-el-5.0-api | before 0:10.1.60-0.1.hum1 | 0:10.1.60-0.1.hum1 |
| Red Hat:hummingbird:1 | tomcat10-jsp-3.1-api | before 0:10.1.60-0.1.hum1 | 0:10.1.60-0.1.hum1 |
| Red Hat:hummingbird:1 | tomcat10-lib | before 0:10.1.60-0.1.hum1 | 0:10.1.60-0.1.hum1 |
| Red Hat:hummingbird:1 | tomcat10-servlet-6.0-api | before 0:10.1.60-0.1.hum1 | 0:10.1.60-0.1.hum1 |
| Red Hat:hummingbird:1 | tomcat10-user-instance | before 0:10.1.60-0.1.hum1 | 0:10.1.60-0.1.hum1 |
| Red Hat:hummingbird:1 | tomcat10-webapps | before 0:10.1.60-0.1.hum1 | 0:10.1.60-0.1.hum1 |
| Red Hat:hummingbird:1 | tomcat11 | before 0:11.0.26-0.1.hum1 | 0:11.0.26-0.1.hum1 |
| Red Hat:hummingbird:1 | tomcat11-admin-webapps | before 0:11.0.26-0.1.hum1 | 0:11.0.26-0.1.hum1 |
| Red Hat:hummingbird:1 | tomcat11-common | before 0:11.0.26-0.1.hum1 | 0:11.0.26-0.1.hum1 |
| Red Hat:hummingbird:1 | tomcat11-docs-webapp | before 0:11.0.26-0.1.hum1 | 0:11.0.26-0.1.hum1 |
| Red Hat:hummingbird:1 | tomcat11-el-6.0-api | before 0:11.0.26-0.1.hum1 | 0:11.0.26-0.1.hum1 |
| Red Hat:hummingbird:1 | tomcat11-jsp-4.0-api | before 0:11.0.26-0.1.hum1 | 0:11.0.26-0.1.hum1 |
| Red Hat:hummingbird:1 | tomcat11-lib | before 0:11.0.26-0.1.hum1 | 0:11.0.26-0.1.hum1 |
+3
Same product
apache software foundation: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-86248Apache Tomcat: Fix for CVE-2026-34500 was incomplete. OCSP checks sometimes soft-fail with FFM even when soft-fail is disabled39Monitor
- CVE-2026-76183Apache Tomcat: Bypass of security constraints for WebSocket endpoints39Monitor
- CVE-2026-86350Apache Tomcat: Regression in fix for CVE-2026-41293 can trigger request header mix-up36Monitor
- CVE-2026-77762Apache Tomcat: Stale HPACK emitter injects trailers into recycled pooled Request32Monitor
- CVE-2026-87022Apache Tomcat: WebSocket message smuggling with per-message-deflate30Monitor
- CVE-2026-79677Apache Tomcat: WebSocket DoS due to lost asynchronous write timeout30Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| Apache Software Foundation Apache Tomcat | 11.0.26 · description | Vendor (CNA) |
| debian:tomcat10 | 10.1.60-1 · Debian:14 | Package registry (OSV) |
| debian:tomcat9 | 9.0.70-2 · Debian:12 | Package registry (OSV) |
| opensuse:tomcat | 9.0.122-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| opensuse:tomcat10 | 10.1.60-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| opensuse:tomcat11 | 11.0.26-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| red hat:tomcat10 | 0:10.1.60-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:tomcat10-admin-webapps | 0:10.1.60-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:tomcat10-common | 0:10.1.60-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:tomcat10-docs-webapp | 0:10.1.60-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:tomcat10-el-5.0-api | 0:10.1.60-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:tomcat10-jsp-3.1-api | 0:10.1.60-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:tomcat10-lib | 0:10.1.60-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:tomcat10-servlet-6.0-api | 0:10.1.60-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:tomcat10-user-instance | 0:10.1.60-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:tomcat10-webapps | 0:10.1.60-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:tomcat11 | 0:11.0.26-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:tomcat11-admin-webapps | 0:11.0.26-0.1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- low · data can be read
- Integrity
- low · data or configuration can be modified
- Availability
- low · the service can be disrupted
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- Low
- Integrity impact
- Low
- Availability impact
- Low
Weakness class (CWE)
CWE-459 · Incomplete CleanupCVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpChange log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- lists.apache.org/thread/qkmsos3s8chn5053qr466rzwv6sk5gjg
- www.openwall.com/lists/oss-security/2026/09/23/26
Vendor advisories and official records. Exploit/PoC links are deliberately left out.