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TI-2026-79987 Aliases CVE-2026-115778GHSA-cwm5-jh59-mwxr

Unauthenticated DoS in Twisted Telnet via Unbounded Buffer

Priority MEDIUM 40CWE-400Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Partial Red Hat: 1 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's twisted.conch.telnet Telnet.dataReceived appends every byte received after IAC SB to a persistent subnegotiation buffer until IAC SE arrives, with no maximum length. Telnet option negotiation happens before authentication, so an unauthenticated peer can omit the terminator and keep growing the buffer. Memory exhaustion can terminate the process and every service it hosts. The weakness is CWE-400, and CISA's SSVC marks the attack as automatable with partial technical impact.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

Description from the CNA

Twisted is an event-based framework for internet applications, supporting Python 3.6+. Prior to 26.10.0rc1, twisted.conch.telnet.Telnet.dataReceived appends every byte received after IAC SB to a persistent subnegotiation buffer until IAC SE is received, without applying a maximum length. Telnet option negotiation occurs before authentication, so an unauthenticated peer can omit the terminator and continuously grow the buffer. The resulting memory exhaustion can terminate the process and every service it hosts. This issue is fixed in version 26.10.0rc1.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0054 45th percentileScored 2026-11-07
Fix Partial twisted (twisted): 26.10.0rc1Twisted (PyPI): 26.10.0rc1Red Hat: 1 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
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-cwm5-jh59-mwxr
  • 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-cwm5-jh59-mwxr

Remediation

Upgrade Twisted (PyPI) to 26.10.0rc1 or later, which fixes the issue. Affected Red Hat Ansible Automation Platform 2 has no fix available.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

  • Fix · CNA twisted (twisted) Fixed in 26.10.0rc1
  • Fix · GHSA-cwm5-jh59-mwxr Twisted (PyPI) Fixed in 26.10.0rc1 Advisory →

Vendor assessments

Red Hat

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

ProductStatusPlan or fix
Red Hat Ansible Automation Platform 2AffectedNo fix yet
Not affected: 2 products
  • Red Hat Ansible Automation Platform 2
  • Red Hat OpenStack Platform 16.2

Timeline

  1. 2026-10-23 Threatist record created from CVE-2026-115778
  2. 2026-10-23 Alias added: GHSA-cwm5-jh59-mwxr
  3. 2026-10-23 Fix available: PyPI/[email protected] · GHSA-cwm5-jh59-mwxr
  4. 2026-10-23 CVSS score added · GHSA-cwm5-jh59-mwxr
  5. 2026-10-23 Weakness changed · GHSA-cwm5-jh59-mwxr
  6. 2026-10-23 6 new references · GHSA-cwm5-jh59-mwxr
  7. 2026-10-24 Priority changed: LOW → MEDIUM
  8. 2026-10-24 Affected versions changed · Red Hat
  9. 2026-10-24 CVSS score added · Red Hat
  10. 2026-10-25 EPSS moved to the below the 50th percentile
  11. 2026-10-29 Affected versions changed · Red Hat

References

Other 6

  • 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