Twisted: Unauthenticated Remote Denial of Service in the Twisted IRC Server via an Unbounded Line Buffer

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-115776: 0.50% estimated exploitation activity in the next 30 days; percentile 42.97 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary An unbounded-buffer vulnerability (CWE-770) in the Twisted words IRC server lets any unauthenticated remote client exhaust server memory. twisted.words.protocols.irc.IRC.dataReceived appends every received byte to a per-connection buffer and only removes data at a line feed, with no maximum length. Because IRC is a plain Protocol and not a LineReceiver, one connection that streams bytes without a line feed grows the buffer without bound and drives the whole single-threaded process to out-of-memory, dropping every user at once. The twistd words server inherits the method unchanged through IRCUser, and the data is buffered before any authentication. Details IRC.dataReceived keeps everything up to the last line feed in self.buffer: With no line feed in the data, lines.pop() returns the entire accumulated content to self.buffer, so it grows by every chunk and is never bounded; IRC defines no MAXLENGTH, no lineLengthExceeded, and no timeout, so the connection is never closed. The…

Published by the source

23 Oct 2026, 20:45 UTC

Last modified by the source

23 Oct 2026, 21:00 UTC

Source last checked

26 Oct 2026, 13:55 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-53xc-49m8-p798

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-53xc-49m8-p798

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-53xc-49m8-p798

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# Patch Next advisory brief: CVE-2026-115776

Advisory: Twisted: Unauthenticated Remote Denial of Service in the Twisted IRC Server via an Unbounded Line Buffer
IDs: CVE-2026-115776, GHSA-53xc-49m8-p798
Record: https://patchnext.com/advisories/cve-2026-115776 (revision 3, source checked 26 Oct 2026, 13:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: twisted 26.10.0rc1. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI twisted: affected <= 26.4.0; fixed in 26.10.0rc1

## Suggested inspection (read-only)
- `python -m pip show twisted`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on twisted.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-53xc-49m8-p798 (GitHub-reviewed advisory GHSA-53xc-49m8-p798 lists affected ranges: PyPI twisted >=0 <=26.4.0)
- Verified: https://osv.dev/vulnerability/GHSA-53xc-49m8-p798 (OSV record GHSA-53xc-49m8-p798 lists affected ranges: PyPI twisted >=0 <26.10.0rc1 (fixed))

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