Twisted is an event-based framework for internet applications, supporting Python 3.6+.

Summary An infinite-loop vulnerability (CWE-835) in the Twisted IMAP4 server lets an authenticated client freeze the whole process with one small command. twisted.mail.imap4.parseNestedParens reads an IMAP literal size with int() and never rejects a negative value. A negative size such as {-100} drives the parser cursor negative, and because a negative Python index wraps around the end of the string instead of raising, the scanning loop never terminates. It runs synchronously on the single-threaded reactor, so one SEARCH command holds the reactor at full CPU forever and every other connection stops being served. Details Meeting an inline literal, parseNestedParens reads the size between the braces and advances the cursor past the body: python twisted/mail/imap4.py parseNestedParens literalSize = int(s[i + 1 : end]) # no sign check contentStack[-1].append((s[end + 3 : end + 3 + literalSize],)) i = end + 3 + literalSize # negative size -> i goes negative int(b"-100") is -100, so i goes negative; the loop condition i < len(s) stays true and s[i : i + 1] on a negative index never raises, so the cursor cycles forever. The literalStringLimit guard only covers the synchronizing-literal…

curl https://cve.zerocrew.in/api/cve/CVE-2026-115774