CVE-2026-4893Network attack vector

Cache manipulation via truncated ECS validation length

Published May 11, 2026 · Updated May 11, 2026

Improper authentication in dnsmasq before 2.92rel2 allows remote attackers to bypass ECS source validation via crafted DNS replies. In process_reply(), find_pseudoheader() replaces the full packet length with the OPT-record length before check_source(), so its first bounds check fails and returns acceptance. The flaw is reachable only when --add-subnet is enabled and an attacker can answer or spoof upstream replies; accepted data can alter subnet-scoped results or expose limited network-topology details.

CVSS severity5.3
Medium
EPSS probability1.78%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper authentication in dnsmasq before 2.92rel2 allows remote attackers to bypass ECS source validation via crafted DNS replies. In process_reply(), find_pseudoheader() replaces the full packet length with the OPT-record length before check_source(), so its first bounds check fails and returns acceptance. The flaw is reachable only when --add-subnet is enabled and an attacker can answer or spoof upstream replies; accepted data can alter subnet-scoped results or expose limited network-topology details.

The record

CVE
CVE-2026-4893
Published
May 11, 2026
Updated
May 11, 2026
Vendor
Simon Kelley
Product
dnsmasq
Classifications
T1565.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 11, 2026CVE publishedPublication date reported by the CVE source.
  2. May 11, 2026Record 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=2.92rel2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Simon Kelley · dnsmasqversion=2.92rel2

Published CVSS scores

5.3CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1565.002Transmitted Data Manipulation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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