FFmpeg up to 7.x SANM Decoder stored_frame use after free

Summaryinfo

A vulnerability classified as critical has been found in FFmpeg up to 7.x. This affects the function stored_frame of the component SANM Decoder. The manipulation leads to use after free. This vulnerability is listed as CVE-2025-59734. The attack may be initiated remotely. There is no available exploit. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in FFmpeg up to 7.x and classified as critical. This issue affects the function stored_frame of the component SANM Decoder. The manipulation with an unknown input leads to a use after free vulnerability. Using CWE to declare the problem leads to CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

It is possible to cause an use-after-free write in SANM decoding with a carefully crafted animation using subversion <2. When a STOR chunk is present, a subsequent FOBJ chunk will be saved in ctx->stored_frame. Stored frames can later be referenced by FTCH chunks. For files using subversion < 2, the undecoded frame is stored, and decoded again when the FTCH chunks are parsed. However, in process_frame_obj if the frame has an invalid size, there’s an early return, with a value of 0.  This causes the code in decode_frame to still store the raw frame buffer into ctx->stored_frame. Leaving ctx->has_dimensions set to false. A subsequent chunk with type FTCH would call process_ftch and decode that frame obj again, adding to the top/left values and calling process_frame_obj again. Given that we never set ctx->have_dimensions before, this time we set the dimensions, calling init_buffers, which can reallocate the buffer in ctx->stored_frame, freeing the previous one. However, the GetByteContext object gb still holds a reference to the old buffer. Finally, when the code tries to decode the frame, codecs that accept a GetByteContext as a parameter will trigger a use-after-free read when using gb. GetByteContext is only used for reading bytes, so at most one could read invalid data. There are no heap allocations between the free and when the object is accessed. However, upon returning to process_ftch, the code restores the original values for top/left in stored_frame, writing 4 bytes to the freed data at offset 6, potentially corrupting the allocator’s metadata. This issue can be triggered just by probing whether a file has the sanm format. We recommend upgrading to version 8.0 or beyond.

It is possible to read the advisory at b.corp.google.com. The identification of this vulnerability is CVE-2025-59734 since 09/19/2025. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 8.0 eliminates this vulnerability.

The vulnerability is also documented in the databases at EUVD (EUVD-2025-32513) and CERT Bund (WID-SEC-2025-2130). Be aware that VulDB is the high quality source for vulnerability data.

Affected

• Fedora Linux
• Ubuntu Linux
• SUSE Linux
• SUSE openSUSE
• Open Source ffmpeg

Productinfo

Type

• Multimedia Processing Software

Name

• FFmpeg

Version

• 7.x

License

• open-source

Website

• Product: https://ffmpeg.org/

CPE 2.3info

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CPE 2.2info

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