Critical

CVE-2026-103119 — Apache Tomcat: AJP response mix-up

Buffer under-read vulnerability in Apache Tomcat meant that a large non-blocking write could result in the response body being split between the current request and the next request received on that connection leading most likely to failure of the second request and possibly leakage of data from the first response to the second. This issue affects Apache Tomcat: from 11.0.0-M25 through 11.0.26. Users are recommended to upgrade to version 11.0.27, which fixes the issue.

Published Oct 20, 2026 · Updated Oct 20, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: apache

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

Technical severity (critical)+10
Automatable exploitation (SSVC)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

—

No EPSS score.

Affects

Apache Software Foundation

Tomcat

CVSS base

9.1

Critical · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

Yes

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Apache Software Foundation Tomcat).
The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Apache Software Foundation	Tomcat	≥ 11.0.0-M25 and ≤ 11.0.26	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
9.1	CVSS 3.1	Critical	3.9	5.2	134c704f-9b21-4f2e-91b3-4a467353bcc0 via NIST National Vulnerability Database
9.1	CVSS 3.1	Critical	—	—	CISA-ADP via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H (score shown at the top: 134c704f-9b21-4f2e-91b3-4a467353bcc0)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-127

Other CVEs with this weakness →

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).

web/proxy/WAF logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first.

2026
Source status changed · Received → Awaiting Analysis
Oct 20, 2026 · NIST National Vulnerability Database
SSVC assessment updated
Oct 20, 2026 · CVE Program (cve.org) e CISA ADP
CVSS changed · 9.1
Oct 20, 2026 · NIST National Vulnerability Database
Record published
Oct 20, 2026
Affected products added · apache software foundation/apache tomcat
Oct 20, 2026 · CVE Program (cve.org) e CISA ADP
Source status changed · → Received
Oct 20, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 20, 2026 · Alertas do Telegram
CVE published
Oct 20, 2026 · apache

Source activity

Repeated readings are counted rather than listed.

2× References added · Oct 20, 2026 – Oct 20, 2026
1× Official description updated · Oct 20, 2026 – Oct 20, 2026

References

2 on the record

lists.apache.org/thread.html/sk2cg4k077fwcqbm6tqz2n700nq06h80
vendor-advisory, NIST National Vulnerability Database
www.openwall.com/lists/oss-security/2026/10/20/28
NIST National Vulnerability Database

Elsewhere on this site

Apache Software Foundation
every CVE for this vendor

CWE-127
other pages naming this weakness

Related CVEs (same products)

Unknown CVE-2026-93446 Apache Tomcat: Possible TLS 1.3 connection failures 12h
Unknown CVE-2026-88041 Apache Tomcat: HTTP/2 trailer header cross-contamination 12h
Unknown CVE-2026-80353 Apache Tomcat: TOCTOU when setting specific permissions for Unix Domain Sockets - Fix for CVE-2026-65183 did not address APR connector 12h
Unknown CVE-2026-74049 Apache Tomcat: Jasper JSTL <c:redirect> plug-in implementation omits page abort (SKIP_PAGE) 12h
Unknown CVE-2026-74048 Apache Tomcat: OpenSSL-FFM FIPS failure does not prevent start-up 12h
Critical CVE-2026-101356 Apache Tomcat: HTTP/2 request/response mix-up after error during async processing 12h

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No FIRST EPSS score.
No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-103119 is "Apache Tomcat: AJP response mix-up", rated Critical. It affects Tomcat (Apache Software Foundation); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 9.1 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

Comments

Moderated technical discussion. Read the community guidelines.

No comments yet.