CVE-2026-125197 PUBLISHED

FFmpeg through 9.0.2 Heap Out-of-Bounds Read via LCL/ZLIB Multithread Decoding

Assigner: VulnCheck
Reserved: 09.11.2026 Published: 09.11.2026 Updated: 09.11.2026

FFmpeg through 9.0.2 contains an integer underflow in decode_frame() in libavcodec/lcldec.c that allows attackers to trigger a heap out-of-bounds read via short ZLIB packets with FLAG_MULTITHREAD. Attackers can supply a crafted AVI or MKV file with an LCL video stream whose packet is shorter than 8 bytes, bypassing length clamping to crash the decoding application.

CVSS Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N
CVSS Score: 6.9

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Local	Confidentiality	Low	Confidentiality	None
Attack Complexity	Low	Integrity	None	Integrity	None
Attack Requirements	None	Availability	High	Availability	None
Privileges Required	None
User Interaction	Passive

CVSS 4.0

CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H
CVSS Score: 6.1

Attack Vector	Local	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	Low
Privileges Required	None	Integrity Impact	None
User Interaction	Required	Availability Impact	High

CVSS 3.1

Product Status

Vendor	FFmpeg
Product	FFmpeg
Versions	Default: unaffected affected from 0 to 9.0.2 (incl.)

CVE-2026-125197 PUBLISHED

FFmpeg through 9.0.2 Heap Out-of-Bounds Read via LCL/ZLIB Multithread Decoding

Metrics

Product Status

Credits

References

Problem Types