CVE-2026-77401 (CVSS 6.8)

Description

Zope AccessControl provides a general security framework for use in Zope. Prior to 7.4, applications that allow untrusted users to create and execute AccessControl-controlled Python code do not safely guard str.format and str.format_map when those methods are reached through a str subclass. In both ImplPython.py and cAccessControl.c, Python formatting can recursively access attributes and subscriptions using unrestricted getattr and getitem behavior instead of the policy-restricted getattr and getitem operations. A controlled format string can therefore disclose objects reachable from values available to the formatting operation. This issue is fixed in version 7.4.

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CVSS v3.1 Score

6.8

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N

EPSS — Exploit Prediction

0.0047

Probability of exploitation

0.39%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-693 CWE-693

References

Other References

https://github.com/zopefoundation/AccessControl/commit/f980450eea416718be62847f34dfd51822938e43 https://github.com/zopefoundation/AccessControl/releases/tag/7.4 https://github.com/zopefoundation/AccessControl/security/advisories/GHSA-pq59-9fq7-m886

Frequently Asked Questions

What is CVE-2026-77401? +

Zope AccessControl provides a general security framework for use in Zope. Prior to 7.4, applications that allow untrusted users to create and execute AccessControl-controlled Python code do not safely guard str.format and str.format_map when those methods are reached through a str subclass. In both ImplPython.py and cAccessControl.c, Python formatting can recursively access attributes and subscriptions using unrestricted getattr and getitem behavior instead of the policy-restricted getattr and getitem operations. A controlled format string can therefore disclose objects reachable from values available to the formatting operation. This issue is fixed in version 7.4. It has a CVSS v3.1 base score of 6.8 (MEDIUM).

How severe is CVE-2026-77401? +

CVE-2026-77401 has a CVSS v3.1 score of 6.8 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0047, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-77401? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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