[FFmpeg-devel] [PATCH] lavf/id3v2: allow empty strings without bom, fixes #20597 (PR #20778)

[Baptiste Coudurier via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #20778 opened by Baptiste Coudurier (bcoudurier)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20778
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20778.patch


>From 1025beeef1d7a46340378f7297ae1399f12d9b99 Mon Sep 17 00:00:00 2001
From: Baptiste Coudurier <baptiste.coudurier@gmail.com>
Date: Tue, 28 Oct 2025 10:59:01 -0700
Subject: [PATCH] lavf/id3v2: allow empty strings without bom, fixes #20597

---
 libavformat/id3v2.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/libavformat/id3v2.c b/libavformat/id3v2.c
index 21a5d2fbf6..3ce2fadce8 100644
--- a/libavformat/id3v2.c
+++ b/libavformat/id3v2.c
@@ -268,7 +268,7 @@ static int decode_str(AVFormatContext *s, AVIOContext *pb, int encoding,
 
     case ID3v2_ENCODING_UTF16BOM:
         if ((left -= 2) < 0) {
-            av_log(s, AV_LOG_ERROR, "Cannot read BOM value, input too short\n");
+            av_log(s, AV_LOG_ERROR, "Cannot read BOM value, input too short %d\n", left);
             ffio_free_dyn_buf(&dynbuf);
             *dst = NULL;
             return AVERROR_INVALIDDATA;
@@ -279,6 +279,11 @@ static int decode_str(AVFormatContext *s, AVIOContext *pb, int encoding,
             get = avio_rl16;
         case 0xfeff:
             break;
+        case 0: // empty string without bom
+            ffio_free_dyn_buf(&dynbuf);
+            *dst = NULL;
+            *maxread = left;
+            return 0;
         default:
             av_log(s, AV_LOG_ERROR, "Incorrect BOM value: 0x%x\n", bom);
             ffio_free_dyn_buf(&dynbuf);
-- 
2.49.1

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