[FFmpeg-devel] [PR] avformat/mpegtsenc: Check remaining space in SDT (PR #21561)

[michaelni via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #21561 opened by michaelni
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21561
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21561.patch

Fixes: out of array access
Fixes: VULN-8

Found-by: Zhenpeng (Leo) Lin from depthfirst
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>


>From e378f617e5fa0d6c321e297c0eaab3ee123baeb8 Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <michael@niedermayer.cc>
Date: Fri, 23 Jan 2026 15:28:58 +0100
Subject: [PATCH] avformat/mpegtsenc: Check remaining space in SDT

Fixes: out of array access
Fixes: VULN-8

Found-by: Zhenpeng (Leo) Lin from depthfirst
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavformat/mpegtsenc.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/libavformat/mpegtsenc.c b/libavformat/mpegtsenc.c
index ea7c6065a0..96cdea955e 100644
--- a/libavformat/mpegtsenc.c
+++ b/libavformat/mpegtsenc.c
@@ -57,6 +57,7 @@ typedef struct MpegTSSection {
     int discontinuity;
     void (*write_packet)(struct MpegTSSection *s, const uint8_t *packet);
     void *opaque;
+    int remaining;
 } MpegTSSection;
 
 typedef struct MpegTSService {
@@ -1018,6 +1019,10 @@ static MpegTSService *mpegts_add_service(AVFormatContext *s, int sid,
         av_log(s, AV_LOG_ERROR, "Too long service or provider name\n");
         goto fail;
     }
+    ts->sdt.remaining -= 10 + service->provider_name[0] + service->name[0];
+    if (ts->sdt.remaining < 0)
+        goto fail;
+
     if (av_dynarray_add_nofree(&ts->services, &ts->nb_services, service) < 0)
         goto fail;
 
@@ -1128,6 +1133,8 @@ static int mpegts_init(AVFormatContext *s)
     // round up to a whole number of TS packets
     ts->pes_payload_size = (ts->pes_payload_size + 14 + 183) / 184 * 184 - 14;
 
+    ts->sdt.remaining    = SECTION_LENGTH - 3;
+
     if (!s->nb_programs) {
         /* allocate a single DVB service */
         if (!mpegts_add_service(s, ts->service_id, s->metadata, NULL))
-- 
2.52.0

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