Bug 2547133 (CVE-2026-106454)

Summary: CVE-2026-106454 twisted: Twisted: Denial of Service via regular expression backtracking in IMAP search patterns
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, dschmidt, eglynn, ikhan, jdelft, jjoyce, jlanda, jpretori, jschluet, jupierce, jwong, kshier, lgarciaa, lhh, mbiarnes, mburns, mgarciac, omaciel, ppalepu, ppostler, prdhamdh, rbobbitt, sghai, sidsharm, simaishi, stcannon, suppawar, ttakamiy, vlaad, yguenane
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Twisted. An authenticated remote attacker can cause a Denial of Service (DoS) by submitting specially crafted mailbox search queries using Internet Message Access Protocol (IMAP) commands such as LIST or LSUB. Because the server fails to properly sanitize these search patterns before compiling them, complex patterns can trigger excessive processing delays known as regular expression catastrophic backtracking. Due to the framework's single-threaded event loop, this blocking operation halts all server traffic, rendering the application unresponsive to other clients.
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Description OSIDB Bzimport 2026-10-06 20:02:25 UTC 
Twisted is an event-based framework for internet applications, supporting Python 3.6+. In 25.5.0 and earlier, wildcardToRegexp() in twisted/mail/imap4.py translates the IMAP asterisk and percent wildcards but passes all other characters from an authenticated client's LIST or LSUB pattern directly to re.compile(), allowing nested or otherwise expensive regular expression constructs to cause catastrophic backtracking when matched against mailbox names. Because Twisted uses a cooperative single-threaded reactor, the blocking match suspends all server input and output for the duration of the match. No fixed release is available as of this review.