PR #21347 opened by Timo Rothenpieler (BtbN) URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21347 Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21347.patch A specially crafted file could define an unlimited number of channels, leading to ever-growing memory allocations and even overflows in the size calculation. Also fixes the not properly checked allocation via av_realloc. Fixes #YWH-PGM40646-33 From 025e88a32c87eaf3e6f912ed51521d020a9a85b2 Mon Sep 17 00:00:00 2001 From: Timo Rothenpieler <timo@rothenpieler.org> Date: Wed, 31 Dec 2025 22:02:34 +0100 Subject: [PATCH 1/2] avcodec/exr: only assign result of av_realloc on allocation success --- libavcodec/exr.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/libavcodec/exr.c b/libavcodec/exr.c index 536a55c5be..8b9fe4b3fc 100644 --- a/libavcodec/exr.c +++ b/libavcodec/exr.c @@ -1603,6 +1603,7 @@ static int decode_header(EXRContext *s, AVFrame *frame) int layer_match = 0; int ret; int dup_channels = 0; + void *tmp; s->current_channel_offset = 0; s->xmin = ~0; @@ -1807,12 +1808,13 @@ static int decode_header(EXRContext *s, AVFrame *frame) } } - s->channels = av_realloc(s->channels, - ++s->nb_channels * sizeof(EXRChannel)); - if (!s->channels) { + tmp = av_realloc(s->channels, ++s->nb_channels * sizeof(EXRChannel)); + if (!tmp) { ret = AVERROR(ENOMEM); goto fail; } + s->channels = tmp; + channel = &s->channels[s->nb_channels - 1]; channel->pixel_type = current_pixel_type; channel->xsub = xsub; -- 2.49.1 From c97c5fa2f3598c14858ec6fb357537ae4fe1c36b Mon Sep 17 00:00:00 2001 From: Timo Rothenpieler <timo@rothenpieler.org> Date: Wed, 31 Dec 2025 22:02:52 +0100 Subject: [PATCH 2/2] avcodec/exr: enforce maximum channel limit to avoid excessive memory allocations A specially crafted file could define an unlimited number of channels, leading to ever growing memory allocations and even overflows in the size calculation. Fixes #YWH-PGM40646-33 --- libavcodec/exr.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/libavcodec/exr.c b/libavcodec/exr.c index 8b9fe4b3fc..10078b462f 100644 --- a/libavcodec/exr.c +++ b/libavcodec/exr.c @@ -59,6 +59,8 @@ #include "mathops.h" #include "thread.h" +#define MAX_CHANNELS 1024 + enum ExrCompr { EXR_RAW, EXR_RLE, @@ -1808,6 +1810,12 @@ static int decode_header(EXRContext *s, AVFrame *frame) } } + if (s->nb_channels >= MAX_CHANNELS) { + av_log(s->avctx, AV_LOG_ERROR, "Number of channels exceeds supported maximum of %d.\n", MAX_CHANNELS); + ret = AVERROR_INVALIDDATA; + goto fail; + } + tmp = av_realloc(s->channels, ++s->nb_channels * sizeof(EXRChannel)); if (!tmp) { ret = AVERROR(ENOMEM); -- 2.49.1