Patch Forecast
Amber warning
Patch this week.

CVE-2026-115778 · GHSA-cwm5-jh59-mwxr

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

Risk score
66/100
CVSS
7.5 v3.1
Exploit chance (30 days)
0.7%
Published
23 Oct 2026

Open in the live forecast Today's forecast

What to know

What it is
Twisted has a vulnerability in its conch Telnet Transport that allows an unauthenticated attacker to cause a denial of service by growing an unbounded subnegotiation buffer. This can lead to memory exhaustion and termination of the process and all services it hosts.
Affected
{'products': ['Twisted'], 'packages': ['Twisted'], 'versions': ['<= 26.4.0']}
Fix
Upgrade to version 26.10.0rc1 or later
Exploitation
No known exploitation

Story map

Story map: TwistedTHE FLAWSTHE FIXCVE-2026-115778Unauthenticated Remote Denialof Service in the Twisted conchTelnet Transport via an…CVSS 7.5 · EPSS 1%CVE-2026-115775Unauthenticated Remote Denialof Service in the Twistedwords domish XML Element…CVSS 8.7 · EPSS 1%CVE-2026-115776Unauthenticated Remote Denialof Service in the Twisted IRCServer via an Unbounded Line…CVSS 7.5 · EPSS 1%CVE-2026-115774Denial of Service in theTwisted IMAP4 Server via aNegative Literal Size in…CVSS 4.9 · EPSS 1%Upgrade Twisted26.10.0or later on your release lineWho is exposed{'products': ['Twisted'],'packages': ['Twisted'],'versions': ['<= 26.4.0']}AMBER · PATCH THIS WEEKTwistedTwisted has a vulnerability in itsXML parser that allows anunauthenticated remote peer tocause a denial of service bycontinuously adding childelements to an in-memory tree,exhausting server memory and…Where it standsNo known exploitationCONNECTS TOSame weaknessDenial of service (CWE-400)250 other warnings in 30 days →
Story map: the flaws, the fix, how it unfolded and what it connects to. Boxes link to the record or article.

At a glance

Twisted: Amber, patch this week. Twisted has a vulnerability in its XML parser that allows an unauthenticated remote peer to cause a denial of service by continuously adding child elements to an in-memory tree, exhausting server memory and terminating the process.

The flaws

  • CVE-2026-115778: Unauthenticated Remote Denial of Service in the Twisted conch Telnet Transport via an Unbounded Subnegotiation Buffer (CVSS 7.5 · EPSS 1%)
  • CVE-2026-115775: Unauthenticated Remote Denial of Service in the Twisted words domish XML Element Stream via an Unbounded Element Tree (CVSS 8.7 · EPSS 1%)
  • CVE-2026-115776: Unauthenticated Remote Denial of Service in the Twisted IRC Server via an Unbounded Line Buffer (CVSS 7.5 · EPSS 1%)
  • CVE-2026-115774: Denial of Service in the Twisted IMAP4 Server via a Negative Literal Size in SEARCH (CVSS 4.9 · EPSS 1%)

The fix

Upgrade Twisted: 26.10.0 or later on your release line

Who is exposed: {'products': ['Twisted'], 'packages': ['Twisted'], 'versions': ['<= 26.4.0']}

Where it stands

  • No known exploitation

Connects to

Why it is Amber

  • CVSS 7.5 high
  • Remotely exploitable without logging in
  • On your watchlist: PyPI

Affected packages

PackageEcosystemVulnerableFixed in
Twistedpip<= 26.4.026.10.0rc1

References

Original 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.

Last activity 23 Oct 2026. Patch Forecast updates every hour.