Apache Tomcat: Buffer Under-read
CVE-2026-103119 is a critical-severity buffer under-read vulnerability in Apache Tomcat from Apache, with a CVSS 3.1 base score of 9.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected Apache Tomcat versions: 11.0.0-M25 through 11.0.26. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.59% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of Apache Tomcat you run against the affected versions below, and install the vendor's latest release.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Apache | Apache Tomcat | 11.0.0-M25 through 11.0.26 | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H. Scored by CISA (ADP).
Official description
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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Buffer Under-read
The product reads from a buffer using buffer access mechanisms such as indexes or pointers that reference memory locations prior to the targeted buffer.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
References
Other references
Other vulnerabilities in Apache Tomcat
- 7.5 High severity
- 7.5 High severity
- 8.1 High severity
- 9.1 Critical severity
- 8.1 High severity
- 7.5 High severity
Recent Buffer Under-read vulnerabilities
- 7.5 High severity
- 9.1 Critical severity
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