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

> An attacker with workspace write access can exploit a race condition to redirect file writes outside the sandbox, potentially escalating privileges or executing code.

- **Severity:** High 7.7 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 7 Oct 2026
- **Updated:** 7 Oct 2026
- **Also known as:** GHSA-5j29-h97v-84ch

## What is CVE-2026-103435?

CVE-2026-103435 is a high-severity path traversal vulnerability in @anthropic-ai/claude-code, published on 7 Oct 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-61 (UNIX Symbolic Link (Symlink) Following), CWE-367 (Time-of-check Time-of-use (TOCTOU) Race Condition), CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-103435?


## How do I fix CVE-2026-103435?

No fix has been published for CVE-2026-103435 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-103435 being exploited?

There is no known exploitation of CVE-2026-103435 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-103435 and fix it if it is affected.

What it is: CVE-2026-103435 is a high-severity path traversal vulnerability in @anthropic-ai/claude-code, published on 7 Oct 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-103435 in the wild and no public exploit code.

Affected product: @anthropic-ai/claude-code. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-103435/ (Markdown: https://insights.sbomify.com/CVE-2026-103435/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-103435
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-103435
- OSV: https://osv.dev/vulnerability/CVE-2026-103435

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-103435/
Summaries are generated and may contain mistakes; the official description above is the record.