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Vulnerability · Published Oct 23, 2026 · Assigned by GitHub_M

CVE-2026-115778Twisted: Unauthenticated Remote Denial of Service in the Twisted conch Telnet Transport via an Unbounded Subnegotiation Buffer

High 7.5

In plain English

A high-severity uncontrolled resource consumption in twisted from twisted. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 46% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High
Exploit odds (30 days)0.5%top 54.4% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12twistedno fix listedDEBIAN-CVE-2026-115778
Debian:13twistedno fix listedDEBIAN-CVE-2026-115778
Debian:14twisted26.10.0-1DEBIAN-CVE-2026-115778
PyPItwisted26.10.0rc1GHSA-cwm5-jh59-mwxr
Ubuntu:22.04:LTStwistedno fix listedUBUNTU-CVE-2026-115778
Ubuntu:24.04:LTStwistedno fix listedUBUNTU-CVE-2026-115778
Ubuntu:26.04:LTStwistedno fix listedUBUNTU-CVE-2026-115778
Ubuntu:26.10twistedno fix listedUBUNTU-CVE-2026-115778

Affected products (as reported)

VendorProductVersions
twisted twisted < 26.10.0rc1

Weakness: CWE-400, CWE-770 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References