# Zope AccessControl vulnerable to information disclosure through Python string \`format\` and \`format_map\` functions

Advisory record · `GHSA-pq59-9fq7-m886`

- **Identifiers:** `GHSA-pq59-9fq7-m886` · `CVE-2026-77401` · `PYSEC-2026-4022`
- **State:** Confirmed
- **Severity:** CVSS 6.8 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-693](https://cwe.mitre.org/data/definitions/693.html)
- **Tags:** [CWE-693](https://agentprime.io/advisories/tag/cwe-693.md)
- **Published:** 17 Sept 2026
- **Updated:** 1 Oct 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 17 Sept 2026, 16:30 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `accesscontrol` (PyPI): affected `<7.4`; fixed in `7.4`

## Machine-written summary

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

> Zope AccessControl (PyPI package accesscontrol) versions before 7.4 are vulnerable to information disclosure through Python's string format and format_map functions, including on subclasses of str. An attacker who can supply a format string in restricted code can read objects reachable through attribute access and subscription, bypassing AccessControl's policy checks. Upgrade to version 7.4, which contains the fix; the source lists no workaround.

Written 1 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

- 6.8 Medium, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0047, the 40th percentile, on 8 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:09 UTC: First seen by agentprime
- 31 Oct 2026, 14:09 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-pq59-9fq7-m886)

## Sources

- [GitHub Advisory Database: GHSA-pq59-9fq7-m886](https://github.com/advisories/GHSA-pq59-9fq7-m886)
- [OSV: GHSA-pq59-9fq7-m886](https://osv.dev/vulnerability/GHSA-pq59-9fq7-m886)
- <https://github.com/zopefoundation/AccessControl/security/advisories/GHSA-pq59-9fq7-m886>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-77401>
- <https://github.com/zopefoundation/AccessControl/commit/f980450eea416718be62847f34dfd51822938e43>
- <https://github.com/zopefoundation/AccessControl>
- <https://github.com/zopefoundation/AccessControl/releases/tag/7.4>

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-pq59-9fq7-m886>, 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/GHSA-pq59-9fq7-m886/>. Everything for agents: <https://agentprime.io/llms.txt>.