CVE-2026-125257 (CVSS 7)

Description

FFmpeg through 9.0.2 contains an off-by-one heap overflow vulnerability in get_exponent_dynamic() in libavcodec/nellymoserenc.c that allows writing one element past the opt and path allocations. Attackers can supply crafted audio to applications encoding Nellymoser with trellis enabled, causing idx to equal OPT_SIZE and overwrite adjacent heap memory.

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CVSS v3.1 Score

7.0

HIGH

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

EPSS — Exploit Prediction

0.0014

Probability of exploitation

0.04%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-193 CWE-193

References

Other References

https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24471 https://github.com/FFmpeg/FFmpeg https://github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/nellymoserenc.c#L262 https://github.com/FFmpeg/FFmpeg/commit/733bec3e19759520ccdbeb6c3c0cae280bbe6dc5 https://www.vulncheck.com/advisories/ffmpeg-through-9.0.2-heap-overflow-via-nellymoser-encoder-trellis-search

Frequently Asked Questions

What is CVE-2026-125257? +

FFmpeg through 9.0.2 contains an off-by-one heap overflow vulnerability in get_exponent_dynamic() in libavcodec/nellymoserenc.c that allows writing one element past the opt and path allocations. Attackers can supply crafted audio to applications encoding Nellymoser with trellis enabled, causing idx to equal OPT_SIZE and overwrite adjacent heap memory. It has a CVSS v3.1 base score of 7.0 (HIGH).

How severe is CVE-2026-125257? +

CVE-2026-125257 has a CVSS v3.1 score of 7.0 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0014, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-125257? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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