CVE-2025-59734
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-10-06

Last updated on: 2025-10-19

Assigner: Google Inc.

Description
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.
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Meta Information
Published
2025-10-06
Last Modified
2025-10-19
Generated
2026-05-07
AI Q&A
2025-10-06
EPSS Evaluated
2026-05-05
NVD
CVE-2025-59734
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
subversion subversion *
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-416 The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability is a use-after-free write issue in SANM decoding in subversion versions less than 2. It occurs when processing certain animation frames: an invalid frame size causes the code to store a raw frame buffer without setting dimensions, leading to a later reallocation that frees the original buffer while a reference to it remains. When the code later tries to decode the frame using this stale reference, it reads freed memory (use-after-free). Additionally, the code writes to the freed memory, potentially corrupting allocator metadata. This can be triggered simply by probing a file for the SANM format.


How can this vulnerability impact me? :

This vulnerability can lead to memory corruption due to use-after-free and write-after-free conditions, which may cause crashes, data corruption, or potentially allow an attacker to execute arbitrary code or cause denial of service when processing crafted SANM animation files.


How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability can be detected by probing whether a file has the sanm format, as the issue can be triggered just by such probing. However, no specific commands or detection tools are provided in the available information.


What immediate steps should I take to mitigate this vulnerability?

The recommended immediate step to mitigate this vulnerability is to upgrade to subversion version 8.0 or beyond.


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