CVE Intelligence
Medium Denial of service

CVE-2026-115774 — Twisted: Denial of Service in the Twisted IMAP4 Server via a Negative Literal Size in SEARCH

Twisted is an event-based framework for internet applications, supporting Python 3.6+. Prior to 26.10.0rc1, twisted.mail.imap4.IMAP4Server reaches twisted.mail.imap4.parseNestedParens with a negative literal size in an authenticated SEARCH command after the client enters the selected mailbox state. The negative size moves the parser cursor below zero, and Python's negative indexing prevents the synchronous scanning loop from terminating. The loop freezes the single-threaded reactor, stopping other IMAP connections and any SMTP or POP3 services hosted in the same process until restart. This issue is fixed in version 26.10.0rc1.

Published Oct 23, 2026 · Updated Oct 29, 2026 · Sources: CVE Program (cve.org) e CISA ADP, NIST National Vulnerability Database, GitHub Security Advisories · CNA: GitHub_M

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 0.4% (30-day exploitation probability)+6
  • Technical severity (medium)+3
  • CISA SSVC: exploitation "poc"+5

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
0.43%
ahead of 37% of scored CVEs · Oct 29, 2026
Affects
Twisted
Twisted
CVSS base
4.9
Medium · 3 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
Proof of concept
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

  • Pip Twisted: fixed in version 26.10.0rc1 — github.com (GitHub Security Advisories)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Twisted Twisted, Pip Twisted).
  2. Apply the fixed version or the patch documented under Remediation.
  3. Search available logs for exploit probes matching the vulnerability class (denial of service), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Twisted Twisted version < 26.10.0rc1 Vulnerable CVE Program (cve.org) e CISA ADP
Pip Twisted ≤ 26.4.0 Vulnerable GitHub Security Advisories

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
Low
Privileges required
High
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
4.9 CVSS 3.1 Medium 1.2 3.6 security-advisories@github.com via NIST National Vulnerability Database
4.9 CVSS 3.1 Medium — — GitHub, Inc. via GitHub Security Advisories
4.9 CVSS 3.1 Medium — — GitHub_M via CVE Program (cve.org) e CISA ADP
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H (score shown at the top: security-advisories@github.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-400 · Uncontrolled Resource Consumption

Other CVEs with this weakness →

EPSS over time FIRST

Oct 24, 2026 → Oct 29, 2026 · 6 reading(s) · max 0.59%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
  • Track CPU/memory spikes and availability drops correlated with request patterns.
web/proxy/WAF logsnetwork IDS/IPSresource metrics

Timeline

What happened to this CVE, newest first.

  • 2026
  • SSVC assessment updated
    Oct 29, 2026 · CVE Program (cve.org) e CISA ADP
  • Source status changed · Received → Awaiting Analysis
    Oct 26, 2026 · NIST National Vulnerability Database
  • Fix documented
    Oct 23, 2026 · GitHub Security Advisories
  • Affected products added · pip/twisted
    Oct 23, 2026 · GitHub Security Advisories
  • Source status changed · Published → Received
    Oct 23, 2026 · NIST National Vulnerability Database
  • Record published
    Oct 23, 2026
  • CVSS changed · 4.9
    Oct 23, 2026 · CVE Program (cve.org) e CISA ADP
  • Source status changed · → Published
    Oct 23, 2026 · CVE Program (cve.org) e CISA ADP
  • Record created in this database
    Oct 23, 2026 · CVE Program (cve.org) e CISA ADP
  • CVE published
    Oct 23, 2026 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

  • 1× References added · Oct 23, 2026 – Oct 23, 2026
  • 1× Official description updated · Oct 23, 2026 – Oct 23, 2026

References

5 on the record

Elsewhere on this site

Twisted
every CVE for this vendor
Denial of service
same class
CWE-400
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-83813 Twisted: DNS Response Spoofing in twisted.names Due to Missing Source Address Validation 6d
  • CVE-2026-115775 Twisted: Unauthenticated Remote Denial of Service in the Twisted words domish XML Element Stream via an Unbounded Element Tree 6d
  • CVE-2026-115776 Twisted: Unauthenticated Remote Denial of Service in the Twisted IRC Server via an Unbounded Line Buffer 6d
  • CVE-2026-115778 Twisted: Unauthenticated Remote Denial of Service in the Twisted conch Telnet Transport via an Unbounded Subnegotiation Buffer 6d
  • CVE-2026-115877 Twisted: HTTP Request Smuggling in twisted.web via a Bare CR or LF in a Header Value 6d
  • CVE-2026-106454 Twisted: IMAP wildcardToRegexp() ReDoS 23d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-115774 is "Twisted: Denial of Service in the Twisted IMAP4 Server via a Negative Literal Size in SEARCH", rated Medium. It affects Twisted (Twisted); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 4.9 describes technical severity. EPSS 0.43% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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