Twisted up to 26.9.x IMAP4 twisted/mail/imap4.py twisted.mail.imap4.parseNestedParens infinite loop

CVSS Meta Temp Score
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CTI Interest Score
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4.5$0-$5k1.22

Summaryinfo

A vulnerability was found in Twisted up to 26.9.x. It has been classified as problematic. The affected element is the function twisted.mail.imap4.parseNestedParens of the file twisted/mail/imap4.py of the component IMAP4. This manipulation causes infinite loop. This vulnerability is registered as CVE-2026-115774. Remote exploitation of the attack is possible. No exploit is available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability classified as problematic was found in Twisted up to 26.9.x. Affected by this vulnerability is the function twisted.mail.imap4.parseNestedParens of the file twisted/mail/imap4.py of the component IMAP4. The manipulation with an unknown input leads to a infinite loop vulnerability. The CWE definition for the vulnerability is CWE-835. The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop. As an impact it is known to affect availability. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-115774 since 10/23/2026. The exploitation appears to be easy. The attack can be launched remotely. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1499 for this issue.

Upgrading to version 26.10.0rc1 eliminates this vulnerability.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Name

Version

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 4.6
VulDB Meta Temp Score: 4.5

VulDB Base Score: 4.3
VulDB Temp Score: 4.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 4.9
CNA Vector (GitHub_M): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Infinite loop
CWE: CWE-835 / CWE-404
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Twisted 26.10.0rc1

Timelineinfo

10/23/2026 Advisory disclosed
10/23/2026 +0 days CVE reserved
10/23/2026 +0 days VulDB entry created
10/23/2026 +0 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: github.com
Status: Confirmed

CVE: CVE-2026-115774 (🔒)
GCVE (CVE): GCVE-0-2026-115774
GCVE (VulDB): GCVE-100-426025

Entryinfo

Created: 10/23/2026 22:42
Changes: 10/23/2026 22:42 (65)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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