# CVE-2026-103435: Arbitrary File Write via Write-Time Symlink Following (TOCTOU) in Claude Code

> CVE-2026-103435: Arbitrary File Write via Write-Time Symlink Following (TOCTOU) in Claude Code. CVSS 7.7 (CVSS 4.0).

Canonical: https://rewindex.com/cve/CVE-2026-103435
Last updated: 2026-10-07T15:16:57Z

- Published: 2026-10-07 12:50 UTC · Updated: 2026-10-07 15:16 UTC · Assigner: Anthropic
- CVSS: 7.7 (CVSS 4.0) · Severity: High
- EPSS: 0.25%, 16th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-22, CWE-367, CWE-61

## Description

Claude Code validated that a target file path resided within the project working directory at permission-check time, but re-resolved the path at write time without repeating that validation. This time-of-check to time-of-use (TOCTOU) gap allowed an attacker who could write to the workspace to atomically replace a project file with a symlink, causing Claude Code to follow the symlink and write its output to an arbitrary file outside the project sandbox. Exploitation required the ability to win a race condition against the write operation and write access to the shared workspace, enabling a lower-privileged attacker to redirect benign edits to sensitive files (e.g., shell configuration) in a higher-privileged session. Users on standard Claude Code auto-update have received this fix already. Users performing manual updates are advised to update to the latest version. Thank you to hackerone.com/c\_h4ck\_0 for reporting this issue.

## Affected vendors and products

- Anthropic: @anthropic-ai/claude-code

## Tracked companies

- [Anthropic](https://rewindex.com/company/anthropic.md)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-103435)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-103435)
- [https://github.com/anthropics/claude-code/security/advisories/GHSA-5j29-h97v-84ch](https://github.com/anthropics/claude-code/security/advisories/GHSA-5j29-h97v-84ch)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2026-103435 · Markdown: https://rewindex.com/cve/CVE-2026-103435.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-103435 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T03:13:38.786Z