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.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
High
Complete denial of service
CVSS Vector v3.1
Weakness Type (CWE)
Vulnerable Products
twisted:twisted
References 5
https://github.com/twisted/twisted/security/advisories/GHSA-cwm5-jh59-mwxr
https://github.com/twisted/twisted/security/advisories/GHSA-cwm5-jh59-mwxr
https://github.com/twisted/twisted/pull/12750
https://github.com/twisted/twisted/pull/12750
https://github.com/twisted/twisted/commit/073ba878c6c07d569cb61abc5ae76d46eff1b…
https://github.com/twisted/twisted/commit/073ba878c6c07d569cb61abc5ae76d46eff1b529
https://github.com/twisted/twisted/commit/5d91cc66a3591faba758a80a1479e0103602f…
https://github.com/twisted/twisted/commit/5d91cc66a3591faba758a80a1479e0103602facc
https://github.com/twisted/twisted/releases/tag/twisted-26.10.0rc1
https://github.com/twisted/twisted/releases/tag/twisted-26.10.0rc1