# CVE-2026-77621: Vector: Arbitrary file write in the file sink via templated path (path traversal).

> Attackers can write arbitrary files outside intended directories via templated paths, potentially leading to code execution or data modification.

- **Severity:** Critical 9.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:H/SI:H/SA:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 22 Sep 2026
- **Updated:** 25 Sep 2026
- **Also known as:** GHSA-6342-xwvw-c637

## What is CVE-2026-77621?

CVE-2026-77621 is a critical path traversal vulnerability in vectordotdev vector, published on 22 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Vector is a high-performance observability data pipeline. From 0.10.0 until 0.57.0, the file sink renders its templated path from event fields and opens the result without confining it to an intended directory. When an untrusted source supplies an event field used by the path template, the value can contain an absolute path or parent-directory traversal, causing Vector to create parent directories and create or overwrite files outside the intended location with the Vector process privileges. The resulting file write can modify sensitive files and can lead to code execution when a scheduled task, authorization file, or subsequently executed script is targeted. This issue is fixed in version 0.57.0.

Weakness: CWE-73 (External Control of File Name or Path), CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-77621?


## How do I fix CVE-2026-77621?

No fix has been published for CVE-2026-77621 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-77621 being exploited?

There is no known exploitation of CVE-2026-77621 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77621 and fix it if it is affected.

What it is: CVE-2026-77621 is a critical path traversal vulnerability in vectordotdev vector, published on 22 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-77621 in the wild and no public exploit code.

Affected product: vectordotdev vector. 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-2026-77621/ (Markdown: https://insights.sbomify.com/CVE-2026-77621/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77621
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77621
- OSV: https://osv.dev/vulnerability/CVE-2026-77621

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-77621/
Summaries are generated and may contain mistakes; the official description above is the record.