Twisted is an event-based framework for internet applications, supporting Python 3.6+.
CVE-2026-115778
Summary An allocation-without-limits vulnerability (CWE-770) in the Twisted conch telnet transport lets any unauthenticated remote peer exhaust server memory over a single connection. When the peer opens a telnet subnegotiation with IAC SB and then streams bytes without ever sending the IAC SE terminator, every byte is appended to a per-connection buffer that has no maximum length. The buffer persists across reads and is released only on the terminator the attacker withholds, so it grows without bound until the process is killed. Details The option-negotiation state machine in Telnet.dataReceived enters the subnegotiation state on IAC SB and sets an empty command list. In that state every non-IAC byte is appended to the list with no length check: python src/twisted/conch/telnet.py (Telnet.dataReceived) elif self.state == "subnegotiation": if b == IAC: self.state = "subnegotiation-escaped" else: self.commands.append(b) # unbounded: no len(self.commands) check self.commands is an instance attribute that persists across dataReceived calls and is deleted only when IAC SE completes the subnegotiation. Negotiation runs at the transport layer before authentication, and the bytes are…
Assessment
- CVSS
- 7.5 (v3.1)
- Severity
- High
- EPSS
- 0.0054% chance of exploitation in the next 30 days
- Known exploited
- Not listed in CISA KEV
- Exploit availability
- Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
- Published
- 23 October 2026
- Last updated
- 26 October 2026
- Affected
- pip · Twisted
- Weakness
- CWE-400, CWE-770
- Assigner
- security-advisories@github.com
CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
At the source
References
- https://github.com/twisted/twisted/commit/073ba878c6c07d569cb61abc5ae76d46eff1b529
- https://github.com/twisted/twisted/commit/5d91cc66a3591faba758a80a1479e0103602facc
- https://github.com/twisted/twisted/pull/12750
- https://github.com/twisted/twisted/releases/tag/twisted-26.10.0rc1
- https://github.com/twisted/twisted/security/advisories/GHSA-cwm5-jh59-mwxr
- https://github.com/advisories/GHSA-cwm5-jh59-mwxr
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