CVE-2025-27091Network attack vector

Decoder crash via SPS allocation race

Published Feb 20, 2025 · Updated Feb 20, 2025

Heap overflow in Cisco OpenH264 2.5.0 and earlier allows remote attackers to crash a decoding client via a crafted H.264 video. The WelsDecodeBs path continued after a non-concealed decoder error; the patch returns before advancing and reusing the destination NAL buffer. A victim must process the malicious video; the confirmed consequence is a client crash, while host command execution is not established.

CVSS severity8.6
High
EPSS probability0.69%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap overflow in Cisco OpenH264 2.5.0 and earlier allows remote attackers to crash a decoding client via a crafted H.264 video. The WelsDecodeBs path continued after a non-concealed decoder error; the patch returns before advancing and reusing the destination NAL buffer. A victim must process the malicious video; the confirmed consequence is a client crash, while host command execution is not established.

The record

CVE
CVE-2025-27091
Published
Feb 20, 2025
Updated
Feb 20, 2025
Vendor
ClamAV
Product
OpenH264
Classifications
CWE-122, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 20, 2025CVE publishedPublication date reported by the CVE source.
  2. Feb 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=< 2.6.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · OpenH264version=< 2.6.0

Published CVSS scores

8.6GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
7.5NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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

CWE-122Heap-based Buffer Overflow
T1203Exploitation for Client Execution

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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