Twisted: Unauthenticated Remote Denial of Service in the Twisted IRC Server via an Unbounded Line Buffer
Only the twistd words IRC server, which uses the IRCUser subclass, is affected in Twisted 26.4.0 and earlier. The fix is in 26.10.0rc1.
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Default setups
- Fix
- Fixed in 26.10.0rc1
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: none
- Automatable: yes
- Technical impact: partial
Summary
The Twisted Python networking framework's IRC server component (twisted.words) can be made to run out of memory by an unauthenticated remote client that sends data without line breaks, which crashes the shared server process and disconnects all users. The flaw affects the IRC protocol handling and the IRC server user implementation, and it is resolved in a newer release.
Summarized by anthropic/claude-haiku-5.5. Verify details against the original sources.
Read the original description
Twisted is an event-based framework for internet applications, supporting Python 3.6+. Prior to 26.10.0rc1, twisted.words.protocols.irc.IRC.dataReceived retains all bytes received without a line feed in its per-connection buffer and applies no maximum line length. The twisted.words.service.IRCUser server subclass inherits this behavior, and buffering occurs before PASS, NICK, or USER authentication commands. An unauthenticated connection can continuously grow the buffer until the shared server process runs out of memory and drops all users. This issue is fixed in version 26.10.0rc1.
Timeline
- CVE published
- First seen by cve.now
- CISA SSVC assessment
Exploitation: none · Automatable: yes · Technical impact: partial
- Record last updated
Affected versions
- twisted twisted
fixed in 26.10.0rc1
- twistedPyPI
fixed in 26.10.0rc1
References 5
Questions about CVE-2026-115776
What does this mean?
An unauthenticated client can open a single connection that makes the IRC server's line buffer grow without limit. This exhausts server memory, crashes the twistd words process, and drops all connected users.Source: github.com
Am I affected, and how do I check?
Twisted 26.4.0 and earlier are affected, specifically the twistd words IRC server that uses the IRCUser subclass. To check, confirm your installed Twisted version and whether the twistd words server is in use.Source: github.com
What should I do about it?
Upgrade Twisted to 26.10.0rc1 or later, which contains the fix.Source: github.com
Is it being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data