CVE-2026-77401: AccessControl Zope AccessControl Vulnerable To Information Vulnerability

MODERATE
Advisory Identifier: GHSA-pq59-9fq7-m886
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CVSS 6.8
CWE-693
Published
Advisory Summary

CVE-2026-77401 is a MODERATE (CVSS 6.8) zope accesscontrol vulnerable to information vulnerability (CWE-693: Protection Mechanism Failure) affecting AccessControl libraries in the PyPI ecosystem. The issue involves zope accesscontrol vulnerable to information disclosure through python string `format` and `format_map` functions. Remediation is available by upgrading affected packages to version 7.4.

CVE-2026-77401 at a Glance

CVE Identifier CVE-2026-77401
GHSA Identifier GHSA-pq59-9fq7-m886
Severity MODERATE
CVSS v3.1 Base Score 6.8
CWE Classification CWE-693: Protection Mechanism Failure
Affected Product AccessControl
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 6.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required High (PR:H)
User Interaction None (UI:N)
Scope Changed (S:C)
Confidentiality High (C:H)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2026-77401

To remediate this vulnerability, upgrade all affected AccessControl dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

AccessControl fixed: 7.4 
pip install AccessControl>=7.4
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show AccessControl

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-77401, inspect your installed packages using pip:

pip show AccessControl

Analyze the terminal output to locate any version of AccessControl in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 7.4), your application is affected.

Note: The pip show AccessControl command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-693: Protection Mechanism Failure, where the product does not use or incorrectly uses a protection mechanism that provides sufficient defense against directed attacks against the product. In AccessControl, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact Python's string `format` functionality allows someone controlling the format string to "read" objects accessible (recursively) via attribute access and subscription from accessible objects. Those attribute accesses and subscriptions use Python's full blown `getattr` and `getitem`, not the policy restricted `AccessControl` variants `_getattr_` and `_getitem_`. This can lead to critical information disclosure. The `AccessControl` package already guards against direct access to the formatting functions on string instances, but these mitigations did not cover subclasses of `str`. Affected are all users who allow untrusted users to create AccessControl controlled Python code and execute it. ### Patches A fix was published with version 7.4. ### Workarounds There is no workaround.

CVE-2026-77401 Affected AccessControl Versions

1 component(s)
Fixed Versions:
7.4
Product / Package Ecosystem Affected Versions Fixed Version
AccessControl
pypi/AccessControl
PyPI
< 7.4
7.4

References

GitHub Advisory / Wiki ADVISORY
https://github.com/zopefoundation/AccessControl/security/advisories/GHSA-pq59-9fq7-m886
NVD — CVE-2026-77401 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-77401
Security Fix Commit FIX COMMIT
https://github.com/zopefoundation/AccessControl/commit/f980450eea416718be62847f34dfd51822938e43
AccessControl Source Repository REPOSITORY
https://github.com/zopefoundation/AccessControl
AccessControl Release RELEASE
https://github.com/zopefoundation/AccessControl/releases/tag/7.4

Frequently Asked Questions

What is CVE-2026-77401?
CVE-2026-77401 is a security vulnerability in AccessControl involving Zope AccessControl vulnerable to information disclosure through Python string `format` and `format_map` functions under CWE-693: Protection Mechanism Failure.
Which AccessControl versions are affected?
Affected versions include releases prior to 7.4 across affected packages: AccessControl.
What version fixes CVE-2026-77401?
Upgrading to 7.4 (or the latest patched release for your respective branch) resolves the vulnerability.
Is AccessControl affected?
Yes, AccessControl is affected in releases prior to 7.4. Upgrade your dependency to 7.4 or later.
What is the CVSS score of CVE-2026-77401?
CVE-2026-77401 has a CVSS v3.1 base score of 6.8 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N.
What CWE is associated with CVE-2026-77401?
CVE-2026-77401 is classified under CWE-693: Protection Mechanism Failure (The product does not use or incorrectly uses a protection mechanism that provides sufficient defense against directed attacks against the product.).
How can I check PyPI dependencies for CVE-2026-77401?
Run the dependency tree command: 'pip show AccessControl'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-pq59-9fq7-m886",
  "modified" : "2026-09-17T16:30:37Z",
  "published" : "2026-09-17T16:30:37Z",
  "aliases" : [ "CVE-2026-77401" ],
  "summary" : "Zope AccessControl vulnerable to information disclosure through Python string `format` and `format_map` functions",
  "details" : "### Impact\nPython's string `format` functionality allows someone controlling the format string to \"read\" objects accessible (recursively) via attribute access and subscription from accessible objects. Those attribute accesses and subscriptions use Python's full blown `getattr` and `getitem`, not the policy restricted `AccessControl` variants `_getattr_` and `_getitem_`. This can lead to critical information disclosure.\n\nThe `AccessControl` package already guards against direct access to the formatting functions on string instances, but these mitigations did not cover subclasses of `str`.\n\nAffected are all users who allow untrusted users to create AccessControl controlled Python code and execute it.\n\n### Patches\nA fix was published with version 7.4.\n\n### Workarounds\nThere is no workaround.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "AccessControl"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "7.4"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/zopefoundation/AccessControl/security/advisories/GHSA-pq59-9fq7-m886"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-77401"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/zopefoundation/AccessControl/commit/f980450eea416718be62847f34dfd51822938e43"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/zopefoundation/AccessControl"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/zopefoundation/AccessControl/releases/tag/7.4"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-693" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-17T16:30:37Z",
    "nvd_published_at" : "2026-09-16T15:17:46Z"
  }
}