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

Quick assessment

Affected
twisted twisted
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Twisted 是一个面向互联网应用的基于事件驱动的框架，支持 Python 3.6 及以上版本。在 26.10.0rc1 之前的版本中，当客户端在已选择邮箱的状态下发送经过身份验证的 SEARCH 命令时， 会调用 ，并传入一个负值的字面量大小。该负值会导致解析器游标移动至零以下，而 Python 的负索引机制使得同步扫描循环无法终止。该循环会冻结单线程的反应器（reactor），从而中断其他 IMAP 连接，并阻止同一进程中托管的任何 SMTP 或 POP3 服务，直至服务重启。此问题已在版本 26.10.0r

CVSS 4.9 · Medium

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2026-115774

Vulnerability Information
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Vulnerability Title
Twisted: Denial of Service in the Twisted IMAP4 Server via a Negative Literal Size in SEARCH
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
twisted twisted < 26.10.0rc1 -

II. Public POCs for CVE-2026-115774

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III. Intelligence Information for CVE-2026-115774

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Patches & Fixes for CVE-2026-115774 (2)

Vendor Advisories for CVE-2026-115774 (1)

Vendor Pages for CVE-2026-115774 (1)

Same Patch Batch · twisted · 2026-10-23 · 6 CVEs total

CVE-2026-115775 8.7 HIGH Twisted: Unauthenticated Remote Denial of Service in the Twisted words domish XML Element
CVE-2026-115776 7.5 HIGH Twisted: Unauthenticated Remote Denial of Service in the Twisted IRC Server via an Unbound
CVE-2026-115778 7.5 HIGH Twisted: Unauthenticated Remote Denial of Service in the Twisted conch Telnet Transport vi
CVE-2026-115877 5.4 MEDIUM Twisted: HTTP Request Smuggling in twisted.web via a Bare CR or LF in a Header Value
CVE-2026-83813 3.1 LOW Twisted: DNS Response Spoofing in twisted.names Due to Missing Source Address Validation

IV. Related Vulnerabilities

Same product: twisted
Same vendor: twisted
Same weakness: CWE-400

V. Comments for CVE-2026-115774

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