# Immutable: Hash-collision algorithmic complexity denial of service in Immutable.Map/Set

Advisory record · `GHSA-xvcm-6775-5m9r`

- **Identifiers:** `GHSA-xvcm-6775-5m9r` · `CVE-2026-59880`
- **State:** Confirmed
- **Severity:** CVSS 8.7 High
- **Critical:** No
- **Weakness (CWE):** [CWE-400](https://cwe.mitre.org/data/definitions/400.html) · [CWE-407](https://cwe.mitre.org/data/definitions/407.html)
- **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md)
- **Published:** 21 Jul 2026
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 21 Jul 2026, 19:02 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `immutable` (npm): affected `>=4.0.0-beta.1, <4.3.9 || >=5.0.0-beta.1, <5.1.8 || <3.8.4`; fixed in `4.3.9`, `5.1.8`, `3.8.4`

## 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

- 8.7 High, CVSS 4.0: `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0066, the 52nd percentile, on 15 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

This record came from the full history of the GitHub Advisory Database, published 21 Jul 2026. New records show when each source confirmed them.

## Sources

- [GitHub Advisory Database: GHSA-xvcm-6775-5m9r](https://github.com/advisories/GHSA-xvcm-6775-5m9r)
- [OSV: GHSA-xvcm-6775-5m9r](https://osv.dev/vulnerability/GHSA-xvcm-6775-5m9r)
- <https://github.com/immutable-js/immutable-js/security/advisories/GHSA-xvcm-6775-5m9r>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-59880>
- <https://github.com/immutable-js/immutable-js/commit/3dd7e5655012597a41873e328bf9142a8901527b>
- <https://github.com/immutable-js/immutable-js/commit/e51d49fc612ded5ec4dfb94ff294d22074269b0f>
- <https://github.com/immutable-js/immutable-js>
- <https://github.com/immutable-js/immutable-js/releases/tag/v3.8.4>
- <https://github.com/immutable-js/immutable-js/releases/tag/v4.3.9>
- <https://github.com/immutable-js/immutable-js/releases/tag/v5.1.8>

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/GHSA-xvcm-6775-5m9r>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

---

The web page: <https://agentprime.io/advisories/GHSA-xvcm-6775-5m9r/>. Everything for agents: <https://agentprime.io/llms.txt>.