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TI-2026-79984 Aliases CVE-2026-115774GHSA-2qrf-pqgx-qh9v

Denial of service in Twisted IMAP4 server via negative SEARCH literal

Priority MEDIUM 56CWE-400Published · Updated

Key facts

Attack vector
Network
Privileges required
High
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Partial Red Hat: 4 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-400.

Summary

Twisted versions before 26.10.0rc1 are affected. A negative literal size in an authenticated SEARCH command after a mailbox is selected makes the IMAP4 parser loop never terminate (CWE-835). An attacker with an authenticated IMAP session can freeze the single-threaded reactor, which blocks other IMAP connections and any SMTP or POP3 services in the same process until restart.

Written with Claude Haiku 5.5 from the sources below · 2026-11-04

Description from the CNA

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.0052 44th percentileScored 2026-11-07
Fix Partial twisted (twisted): 26.10.0rc1Twisted (PyPI): 26.10.0rc1Red Hat: 4 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
twistedtwistedbefore 26.10.0rc126.10.0rc1Patch availableCNA
—Twisted (PyPI)before 26.10.0rc126.10.0rc1Patch availableGHSA-2qrf-pqgx-qh9v
  • twisted Vendortwisted Affected before 26.10.0rc1 Fixed in 26.10.0rc1 Patch available CNA
  • Twisted (PyPI) Vendor— Affected before 26.10.0rc1 Fixed in 26.10.0rc1 Patch available GHSA-2qrf-pqgx-qh9v

Remediation

Upgrade Twisted to version 26.10.0rc1, which fixes this issue. Red Hat lists Red Hat Ansible Automation Platform 2, Red Hat Enterprise Linux 6 and Red Hat OpenStack Platform 13 (Queens) with no fix available, and Red Hat OpenStack Platform 16.2 with no fix planned.

Written with Claude Haiku 5.5 from the sources below · 2026-11-04

  • Fix · CNA twisted (twisted) Fixed in 26.10.0rc1
  • Fix · GHSA-2qrf-pqgx-qh9v Twisted (PyPI) Fixed in 26.10.0rc1 Advisory →

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Ansible Automation Platform 2AffectedNo fix yet: Fix deferred
Red Hat Enterprise Linux 6AffectedNo fix yet: Fix deferred
Red Hat OpenStack Platform 13 (Queens)AffectedNo fix yet: Fix deferred
Red Hat OpenStack Platform 16.2AffectedNo fix planned: Out of support scope

Timeline

  1. 2026-10-23 Threatist record created from CVE-2026-115774
  2. 2026-10-23 Alias added: GHSA-2qrf-pqgx-qh9v
  3. 2026-10-23 Fix available: PyPI/[email protected] · GHSA-2qrf-pqgx-qh9v
  4. 2026-10-23 CVSS score added · GHSA-2qrf-pqgx-qh9v
  5. 2026-10-23 Weakness changed · GHSA-2qrf-pqgx-qh9v
  6. 2026-10-23 5 new references · GHSA-2qrf-pqgx-qh9v
  7. 2026-10-24 Affected versions changed · Red Hat
  8. 2026-10-24 CVSS score added · Red Hat
  9. 2026-10-29 CISA SSVC decision points changed
  10. 2026-10-29 Priority changed: LOW → MEDIUM
  11. 2026-11-04 Affected versions changed · Red Hat

References

Other 5

  • TI-2026-79985 Unauthenticated memory exhaustion in Twisted domish XML parser CVSS 4.0HIGH 8.7
  • TI-2026-30612 Twisted: Denial of Service (DoS) in twisted.names via Crafted DNS Compression Pointer Chains CVSS 3.1HIGH 7.5
  • TI-2022-06090 Buffer Overflow in Twisted CVSS 3.1HIGH 7.5
  • TI-2024-27732 twisted.web has disordered HTTP pipeline response CVSS 3.1HIGH 8.3
  • TI-2024-27854 HTML injection in HTTP redirect body CVSS 3.1MEDIUM 6.1
  • TI-2026-79989 HTTP request smuggling in Twisted web via bare CR or LF in headers CVSS 3.1MEDIUM 5.4
See all 21 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences