# \`append-only-vec\` 0.1.9 was removed from crates.io due to a malicious dependency

Advisory record · `RUSTSEC-2026-0262`

- **Identifiers:** `RUSTSEC-2026-0262`
- **State:** Confirmed
- **Severity:** No CVSS score
- **Critical:** No
- **Published:** 20 Aug 2026
- **Updated:** 20 Oct 2026
- **Reviewed by a person:** No

Published by OSV at 20 Aug 2026, 12:00 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `append-only-vec` (crates.io): affected `>=0.1.9, <0.1.10-0`; fixed in `0.1.10-0`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> Versions of append-only-vec from 0.1.9 up to but not including 0.1.10-0 are affected. A published version depended on a malicious proc-macro1 package whose build script runs attacker code, so building that version can run malicious code. Upgrade to append-only-vec 0.1.10-0 and remove 0.1.9 if it is present.

Written 3 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

No source has published a CVSS score for this record yet.

- **CISA KEV:** Not listed.
- **EPSS:** No score.

## Timeline

- 31 Oct 2026, 14:24 UTC: First seen by agentprime
- 31 Oct 2026, 14:24 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/RUSTSEC-2026-0262)

## Sources

- [OSV: RUSTSEC-2026-0262](https://osv.dev/vulnerability/RUSTSEC-2026-0262)
- <https://crates.io/crates/append-only-vec>
- <https://rustsec.org/advisories/RUSTSEC-2026-0262.html>
- <https://blog.rust-lang.org/2026/08/20/supply-chain-attack-on-arrayref>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/RUSTSEC-2026-0262>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/RUSTSEC-2026-0262/>. Everything for agents: <https://agentprime.io/llms.txt>.