How the CVE Works
CVE-2025-27091 is a heap overflow vulnerability in OpenH264, a widely used H.264 codec library. The flaw occurs due to a race condition between Sequence Parameter Set (SPS) memory allocation and non-IDR NAL unit processing. When decoding a maliciously crafted video bitstream, improper memory handling allows an attacker to overwrite heap data. This can lead to arbitrary code execution or application crashes. The vulnerability affects both SVC and AVC modes in OpenH264 versions ≤ 2.5.0. Attackers exploit this by embedding a malformed bitstream in a video file, triggering heap corruption when processed by the victim’s decoder.
DailyCVE Form
Platform: OpenH264
Version: ≤ 2.5.0
Vulnerability: Heap overflow
Severity: Critical
Date: 05/06/2025
What Undercode Say:
Exploitation:
- Craft a malicious H.264 bitstream with malformed SPS and non-IDR NAL units.
- Embed it in a video container (e.g., MP4).
3. Distribute via phishing or compromised media.
Protection:
1. Upgrade to OpenH264 ≥ 2.6.0.
2. Validate bitstreams before decoding.
3. Use heap hardening (e.g., ASLR, CFG).
Detection Commands:
Check OpenH264 version: pkg-config --modversion openh264
PoC Code (Conceptual):
// Malicious SPS/NAL generator (simplified)
void craft_exploit() {
uint8_t sps = create_malformed_sps();
uint8_t nal = create_corrupt_nonidr();
write_to_file("exploit.h264", sps, nal);
}
Mitigation Code:
// Safe SPS parsing patch (example)
void parse_sps_fixed(uint8_t data) {
if (data == NULL) abort();
size_t alloc_size = validate_sps_size(data);
void buf = malloc(alloc_size);
if (!buf) abort();
}
Analytics:
- CVSS: 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H)
- Exploitability: High (no auth required).
- Patch urgency: Immediate.
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
