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Git pushed a commit to branch release/5.1
in repository ffmpeg.

commit 115ff6126a674d54ee915cba29ea06bdc27335b4
Author:     Oliver Chang <[email protected]>
AuthorDate: Tue Feb 3 05:36:52 2026 +0000
Commit:     Michael Niedermayer <[email protected]>
CommitDate: Tue May 5 15:20:59 2026 +0200

    avcodec/qdm2: fix heap-use-after-free in qdm2_decode_frame
    
    The `sub_packet` index in `QDM2Context` was not reset to 0 when
    `qdm2_decode_frame` started processing a new packet. If an error
    occurred during the decoding of a previous packet, `sub_packet` would
    retain a non-zero value.
    
    In subsequent calls to `qdm2_decode_frame` with a new packet, this
    non-zero `sub_packet` value caused `qdm2_decode` to skip
    `qdm2_decode_super_block`. This function is responsible for initializing
    packet lists with pointers to the current packet's data. Skipping it led
    to the use of stale pointers from the previous (freed) packet, resulting
    in a heap-use-after-free vulnerability.
    
    This patch explicitly resets `s->sub_packet = 0` at the beginning of
    `qdm2_decode_frame`, ensuring correct initialization for each new
    packet.
    
    Fixes: OSS-Fuzz issue 476179569
    (https://issues.oss-fuzz.com/issues/476179569).
    
    (cherry picked from commit a795ca89fa2f49f80cbe7a9fa323f278abf62e7f)
    Signed-off-by: Michael Niedermayer <[email protected]>
---
 libavcodec/qdm2.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libavcodec/qdm2.c b/libavcodec/qdm2.c
index 427e8e8449..71ce66d38b 100644
--- a/libavcodec/qdm2.c
+++ b/libavcodec/qdm2.c
@@ -1852,6 +1852,8 @@ static int qdm2_decode_frame(AVCodecContext *avctx, 
AVFrame *frame,
     if(buf_size < s->checksum_size)
         return -1;
 
+    s->sub_packet = 0;
+
     /* get output buffer */
     frame->nb_samples = 16 * s->frame_size;
     if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)

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