CVE-2026-120246 (CVSS 5.5)

Description

FFmpeg 4.4 through 9.0.2 contains a use of uninitialized variable vulnerability in the CDXL decoder that leaks stack memory into decoded pixels via unfilled HAM palette entries. Attackers can craft a type-0 CDXL file whose HAM pixels select unfilled new_palette entries in cdxl_decode_ham8() or cdxl_decode_ham6(), exposing stack bytes and pointer fragments in the BGR24 output.

Is your site exposed to CVE-2026-120246?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

5.5

MEDIUM

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

Weakness Type (CWE)

CWE-457 CWE-457

References

Other References

https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24856 https://github.com/FFmpeg/FFmpeg https://github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/cdxl.c#L226-L229 https://github.com/FFmpeg/FFmpeg/commit/47313ad3f9f33b892384b976fb7c09b3c85fd74e https://www.vulncheck.com/advisories/ffmpeg-4.4-through-9.0.2-uninitialized-memory-disclosure-via-cdxl-ham-decoder

Frequently Asked Questions

What is CVE-2026-120246? +

FFmpeg 4.4 through 9.0.2 contains a use of uninitialized variable vulnerability in the CDXL decoder that leaks stack memory into decoded pixels via unfilled HAM palette entries. Attackers can craft a type-0 CDXL file whose HAM pixels select unfilled new_palette entries in cdxl_decode_ham8() or cdxl_decode_ham6(), exposing stack bytes and pointer fragments in the BGR24 output. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2026-120246? +

CVE-2026-120246 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

How do I check if I'm vulnerable to CVE-2026-120246? +

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.

Related Vulnerabilities

CVE-2025-26383

The iSTAR Configuration Utility (ICU) tool leaks memory, which could result in the unintended exposure of unauthorized data from the …

CVE-2025-10021

A Use of Uninitialized Variable vulnerability exists in Open Design Alliance Drawings SDK static versions (mt) before 2026.12. Static object …

CVE-2026-18397

This vulnerability enables unauthenticated remote code execution (RCE) on a victim's machine by exploiting a combination of cryptographic weaknesses and …

CVE-2026-66859

NULL Pointer Dereference, Use of Uninitialized Variable vulnerability in Apache Thrift c_glib bindings. This issue affects Apache Thrift: before 0.25.0. …

CVE-2026-112898

Pillow is a Python imaging library. From 9.1.0 until 13.0.0, Pillow can disclose uninitialized stack memory when Image.quantize() uses an …

CVE-2026-112893

Pillow is a Python imaging library. From 10.0.0 until 13.0.0, Pillow can free an invalid glyph pointer during FreeType rendering …

CVE-2026-120246