CVE-2026-115778: Twisted: Unauthenticated Remote Denial of Service in the Twisted conch Telnet Transport via an Unbounded Subnegotiation Buffer
Vulnerability summary
CVE-2026-115778 is a high (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in twisted. EPSS estimates a 0.54% chance of exploitation in the next 30 days, higher than 45.5% of scored vulnerabilities.
Severe, CVSS 7.5 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 1% (FIRST, 03-11-2026)
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 1 · Related 1Timeline
- 23-10-2026PublishedVulnerability first disclosed.
- 23-10-2026Last modifiedVulnerability information updated.
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.
CVSS metrics
6 scores · 6 sources · 1 version- NVDNIST7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · PypiEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · ChainguardEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.54%
Chance of exploitation in the next 30 days
Percentile
46%
Versus all other CVEs
30-day change
Change unavailable
Change unavailable
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-400Uncontrolled Resource ConsumptionThe product does not properly control the allocation and maintenance of a limited resource.
- CWE-770Allocation of Resources Without Limits or ThrottlingThe product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.
Affected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Chainguard2 products
- awxAll versions (No fix recorded)
- synapseAll versions (No fix recorded) | < 1.164.1-r2
Debian1 product
- twistedAll versions (No fix recorded) | < 26.10.0-1
PyPI1 product
- twisted< 26.10.0rc1
Twisted1 product
- twisted< 26.10.0rc1
Ubuntu1 product
- twistedAll versions (No fix recorded)
5 vendors · 6 products
References
11 links- github.com/twisted/twisted/security/advisories/GHSA-cwm5-jh59-mwxrX Refsource CONFIRMWEBREPORTAdvisory
- github.com/twisted/twisted/commit/073ba878c6c07d569cb61abc5ae76d46eff1b529X Refsource MISCWEBREPORTFIX
- github.com/twisted/twisted/commit/5d91cc66a3591faba758a80a1479e0103602faccX Refsource MISCWEBREPORTFIX
- github.com/twisted/twistedPACKAGE
