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.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
High
Admin privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
High
Complete denial of service
CVSS Vector v3.1
Weakness Type (CWE)
Vulnerable Products
twisted:twisted
References 4
https://github.com/twisted/twisted/security/advisories/GHSA-2qrf-pqgx-qh9v
https://github.com/twisted/twisted/security/advisories/GHSA-2qrf-pqgx-qh9v
https://github.com/twisted/twisted/pull/12764
https://github.com/twisted/twisted/pull/12764
https://github.com/twisted/twisted/commit/3d125548bcbe955007cb97f480bb699a5e074…
https://github.com/twisted/twisted/commit/3d125548bcbe955007cb97f480bb699a5e074741
https://github.com/twisted/twisted/releases/tag/twisted-26.10.0rc1
https://github.com/twisted/twisted/releases/tag/twisted-26.10.0rc1