CVE-2026-41080

Denial of service via low-entropy SipHash salt

Published Apr 16, 2026 · Updated Apr 16, 2026

Denial of service in Expat Project libexpat before 2.8.0 allows context-dependent attackers to consume CPU via crafted XML. Expat's hash-flooding defense seeds SipHash with only 4 to 8 bytes even though its implementation supports a 16-byte salt. Reachability depends on an embedding application parsing attacker-controlled XML; the result is prolonged CPU consumption rather than data access or modification.

CVSS severity2.9
Low
EPSS probability0.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Expat Project libexpat before 2.8.0 allows context-dependent attackers to consume CPU via crafted XML. Expat's hash-flooding defense seeds SipHash with only 4 to 8 bytes even though its implementation supports a 16-byte salt. Reachability depends on an embedding application parsing attacker-controlled XML; the result is prolonged CPU consumption rather than data access or modification.

The record

CVE
CVE-2026-41080
Published
Apr 16, 2026
Updated
Apr 16, 2026
Vendor
Expat Project
Product
libexpat
Classifications
CWE-331, T1499.004
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 16, 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=0 <2.7.6

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Expat Project · libexpatversion=0 <2.7.6

Published CVSS scores

2.9MITRECVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A: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)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-331Insufficient Entropy
T1499.004Application or System Exploitation

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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