CVE-2025-27091

High

Published: 20 February 2025

Published

20 February 2025

Modified

06 May 2025

KEV Added

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Patch

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CVSS Score 7.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS Score 0.0247 85.4th percentile

Risk Priority 16 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2025-27091 is a high-severity Heap-based Buffer Overflow (CWE-122) vulnerability in Cisco Openh264. Its CVSS base score is 7.5 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Client Execution (T1203); ranked in the top 14.6% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 SI-2 (Flaw Remediation) and SI-10 (Information Input Validation).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploitation for Client Execution (T1203). What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-2 Flaw Remediation good match

prevent

Directly requires timely remediation of known software flaws by patching OpenH264 to version 2.6.0 or later, eliminating the heap overflow race condition.

SI-16 Memory Protection partial match

prevent

Implements memory safeguards such as address space layout randomization and non-executable heap to mitigate exploitation of the heap overflow for arbitrary command execution.

SI-10 Information Input Validation partial match

prevent

Validates malformed H.264 bitstreams containing crafted SPS and non-IDR NAL units before decoding to prevent triggering the race condition.

MITRE ATT&CK Enterprise TechniquesAI

T1203 Exploitation for Client Execution Execution

Adversaries may exploit software vulnerabilities in client applications to execute code.

attack.mitre.org →

Why these techniques?

Heap overflow in OpenH264 decoder enables remote code execution via crafted malicious video bitstream processed by victim client application, directly mapping to Exploitation for Client Execution.

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

NVD Description

OpenH264 is a free license codec library which supports H.264 encoding and decoding. A vulnerability in the decoding functions of OpenH264 codec library could allow a remote, unauthenticated attacker to trigger a heap overflow. This vulnerability is due to a…

race condition between a Sequence Parameter Set (SPS) memory allocation and a subsequent non Instantaneous Decoder Refresh (non-IDR) Network Abstraction Layer (NAL) unit memory usage. An attacker could exploit this vulnerability by crafting a malicious bitstream and tricking a victim user into processing an arbitrary video containing the malicious bistream. An exploit could allow the attacker to cause an unexpected crash in the victim's user decoding client and, possibly, perform arbitrary commands on the victim's host by abusing the heap overflow. This vulnerability affects OpenH264 2.5.0 and earlier releases. Both Scalable Video Coding (SVC) mode and Advanced Video Coding (AVC) mode are affected by this vulnerability. OpenH264 software releases 2.6.0 and later contained the fix for this vulnerability. Users are advised to upgrade. There are no known workarounds for this vulnerability. ### For more information If you have any questions or comments about this advisory: * [Open an issue in cisco/openh264](https://github.com/cisco/openh264/issues) * Email Cisco Open Source Security ([oss-security@cisco.com](mailto:oss-security@cisco.com)) and Cisco PSIRT ([psirt@cisco.com](mailto:psirt@cisco.com)) ### Credits: * **Research:** Octavian Guzu and Andrew Calvano of Meta * **Fix ideation:** Philipp Hancke and Shyam Sadhwani of Meta * **Fix implementation:** Benzheng Zhang (@BenzhengZhang) * **Release engineering:** Benzheng Zhang (@BenzhengZhang)

Deeper analysisAI

CVE-2025-27091 is a heap overflow vulnerability in the decoding functions of the OpenH264 codec library, which supports H.264 encoding and decoding under a free license. The issue stems from a race condition between Sequence Parameter Set (SPS) memory allocation and subsequent non-Instantaneous Decoder Refresh (non-IDR) Network Abstraction Layer (NAL) unit memory usage. It affects OpenH264 versions 2.5.0 and earlier, impacting both Scalable Video Coding (SVC) mode and Advanced Video Coding (AVC) mode.

A remote, unauthenticated attacker can exploit this vulnerability by crafting a malicious bitstream and tricking a victim into processing an arbitrary video containing it. Successful exploitation may cause an unexpected crash in the victim's decoding client and, by abusing the heap overflow, potentially enable arbitrary command execution on the victim's host. The CVSS v3.1 base score is 7.5 (AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H), with associated CWEs-122 (Heap-based Buffer Overflow) and CWE-787 (Out-of-bounds Write).

Advisories recommend upgrading to OpenH264 releases 2.6.0 or later, which contain the fix. There are no known workarounds. For details, see the GitHub security advisory at https://github.com/cisco/openh264/security/advisories/GHSA-m99q-5j7x-7m9x and the release notes at https://github.com/cisco/openh264/releases/tag/v2.6.0.