CVE-2026-115774

Twisted is an event-based framework for internet applications, supporting Python 3.6+. Prior to 26.10.0rc1, twisted.mail.imap4.IMAP4Server reaches twisted.mail.imap4.parseNestedParens with a negative literal size in an authenticated SEARCH command after the client enters the selected mailbox state. The negative size moves the parser cursor below zero, and Python's negative indexing prevents the synchronous scanning loop from terminating. The loop freezes the single-threaded reactor, stopping other IMAP connections and any SMTP or POP3 services hosted in the same process until restart. This issue is fixed in version 26.10.0rc1.

CVSS 3.1

4.9CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H

EPSS

0.4% chance of exploitation in the next 30 days; higher than 37% of CVEs (scores of 2026-10-25)

CWEs

CWE-400, CWE-835

Published

2026-10-23

Modified

2026-10-23

Record from

the NVD, synced 2026-10-24

Packages (OSV)

References

• https://github.com/twisted/twisted/commit/3d125548bcbe955007cb97f480bb699a5e074741
• https://github.com/twisted/twisted/pull/12764
• https://github.com/twisted/twisted/releases/tag/twisted-26.10.0rc1
• https://github.com/twisted/twisted/security/advisories/GHSA-2qrf-pqgx-qh9v

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