Openh264Application · Cisco
CVE-2025-27091
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedOpenH264 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 ([[email protected]](mailto:[email protected])) and Cisco PSIRT ([[email protected]](mailto:[email protected])) ### 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)
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceHeap overflow vulnerability in OpenH264's decoding functions caused by a race condition between Sequence Parameter Set (SPS) memory allocation and subsequent non-IDR NAL unit memory usage. Attackers can exploit this by crafting malicious video bitstreams to trigger heap corruption, potentially leading to arbitrary command execution.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Openh264Application
< 2.5.1CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- High
- Privileges
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Locate OpenH264 library in the environmentSearch for libopenh264 shared library files: find / -name 'libopenh264*' 2>/dev/null on Linux, or check common paths like C:\Windows\System32\ on Windows. Also check if any applications bundle OpenH264 in their own directories.Affected if OpenH264 library is present on the system
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Determine installed OpenH264 versionRun 'strings libopenh264.so.2 | grep -i version' or check the library filename which often contains the version (e.g., libopenh264.so.2.5.0). Alternatively, check the product documentation or the application that bundles it.Affected if Version is lower than 2.5.1 (e.g., 2.5.0, 2.4.x, 2.3.x, etc.) or version cannot be determined but library exists
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Identify applications using OpenH264 for decodingReview running processes or application configurations that decode H.264 video streams. Common applications include video players, conferencing software, transcoders, and WebRTC implementations.Affected if Applications decode H.264 video using OpenH264 library and version is < 2.5.1
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Check for processing of SPS and non-IDR NAL unitsMonitor or audit video bitstream processing. The vulnerability triggers when SPS memory allocation races with non-IDR NAL unit memory usage during decoding.Affected if The library decodes video bitstreams containing SPS (Sequence Parameter Set) and non-IDR NAL units, which is standard H.264 decoding
A user is affected if OpenH264 library version < 2.5.1 is installed and is being used to decode H.264 video bitstreams, as the race condition in SPS allocation can trigger heap corruption during normal decoding operations.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped2.5.1
Upgrade to OpenH264 version 2.6.0 or later. No workarounds exist; all earlier versions through 2.5.0 are affected in both SVC and AVC modes.
OpenH264 2.6.0 or later
- Identify the current OpenH264 version in use by checking the library binary or dependency manifest
- Download OpenH264 version 2.6.0 or later from the official Cisco OpenH264 GitHub repository (https://github.com/cisco/openh264/releases)
- Replace the existing OpenH264 library binary with the version 2.6.0 or later
- Rebuild or recompile any applications that link against OpenH264 to ensure they use the updated library
- Verify the upgrade by checking that the library version reports 2.6.0 or later
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Openh264
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 h
- Testing8.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-27091 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2025-27091 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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