CVE-2025-11678

Code execution via cumulative DNS label overflow

Published Oct 20, 2025 · Updated Oct 20, 2025

Stack overflow in Warmcat libwebsockets 4 through 4.4.2 allows man-in-the-middle attackers to overwrite memory via forged DNS responses. The lws_adns_parse_label function checks each DNS label substring against the destination size but fails to include bytes copied from earlier substrings, so a segmented oversized label overruns label_stack. Exploitation requires LWS_WITH_SYS_ASYNC_DNS at build time and visibility of a DNS request to forge a matching transaction ID; the overwrite crashes the linked application or enables code execution depending on platform and compiler protections.

CVSS severity7.5
High
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack overflow in Warmcat libwebsockets 4 through 4.4.2 allows man-in-the-middle attackers to overwrite memory via forged DNS responses. The lws_adns_parse_label function checks each DNS label substring against the destination size but fails to include bytes copied from earlier substrings, so a segmented oversized label overruns label_stack. Exploitation requires LWS_WITH_SYS_ASYNC_DNS at build time and visibility of a DNS request to forge a matching transaction ID; the overwrite crashes the linked application or enables code execution depending on platform and compiler protections.

The record

CVE
CVE-2025-11678
Published
Oct 20, 2025
Updated
Oct 20, 2025
Vendor
libwebsockets
Product
libwebsockets
Classifications
CWE-121
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 20, 2025CVE publishedPublication date reported by the CVE source.
  2. Oct 20, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=4.0 <=4.3.6
  2. Affected versionversion=4.0 <=4.4.2

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

libwebsockets · libwebsocketsversion=4.0 <=4.3.6; version=4.0 <=4.4.2

Published CVSS scores

7.5Nozomi Networks Inc.CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-121Stack-based Buffer Overflow

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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