Command: /mnt/scratch0/clusterfuzz/resources/platform/linux/unshare -c -n /mnt/scratch0/clusterfuzz/bot/builds/clusterfuzz-builds_libheif_8acad7d454c394a82b46ab1851e1bcf3f3561254/revisions/encoder_fuzzer -rss_limit_mb=2560 -timeout=60 -runs=100 /mnt/scratch0/clusterfuzz/bot/inputs/fuzzer-testcases/crash-f978831955a96bc7982ff4c885360cd37d1b7904
Time ran: 0.25948143005371094
INFO: Running with entropic power schedule (0xFF, 100).
INFO: Seed: 107110384
INFO: Loaded 1 modules (815934 inline 8-bit counters): 815934 [0x555658a13e40, 0x555658adb17e),
INFO: Loaded 1 PC tables (815934 PCs): 815934 [0x555658adb180,0x55565974e560),
/mnt/scratch0/clusterfuzz/bot/builds/clusterfuzz-builds_libheif_8acad7d454c394a82b46ab1851e1bcf3f3561254/revisions/encoder_fuzzer: Running 1 inputs 100 time(s) each.
Running: /mnt/scratch0/clusterfuzz/bot/inputs/fuzzer-testcases/crash-f978831955a96bc7982ff4c885360cd37d1b7904
/work/x265/source/encoder/frameencoder.cpp:201:9: runtime error: passing zero to __builtin_clz(), which is not a valid argument
#0 0x555655d88152 in x265::FrameEncoder::init(x265::Encoder*, int, int) /work/x265/source/encoder/frameencoder.cpp:201:9
#1 0x555655c34865 in x265::Encoder::create() /work/x265/source/encoder/encoder.cpp:504:33
#2 0x555655ad8746 in x265_encoder_open_216 /work/x265/source/encoder/api.cpp:195:14
#3 0x555655a98364 in x265_start_sequence_encoding_intern(void*, heif_image const*, heif_image_input_class, unsigned int, unsigned int, heif_sequence_encoding_options const*, bool) libheif/libheif/plugins/encoder_x265.cc:1033:22
#4 0x555655a945c0 in x265_encode_image(void*, heif_image const*, heif_image_input_class) libheif/libheif/plugins/encoder_x265.cc:1190:9
#5 0x5556559c8c0a in Encoder_HEVC::encode(std::__1::shared_ptr<HeifPixelImage> const&, heif_encoder*, heif_encoding_options const&, heif_image_input_class) libheif/libheif/codecs/hevc_enc.cc:45:20
#6 0x555655697518 in ImageItem::encode(std::__1::shared_ptr<HeifPixelImage> const&, heif_encoder*, heif_encoding_options const&, heif_image_input_class) libheif/libheif/image-items/image_item.cc:549:19
#7 0x55565568eb10 in ImageItem::encode_to_bitstream_and_boxes(std::__1::shared_ptr<HeifPixelImage> const&, heif_encoder*, heif_encoding_options const&, heif_image_input_class) libheif/libheif/image-items/image_item.cc:251:50
#8 0x555655692f93 in ImageItem::encode_to_item(HeifContext*, std::__1::shared_ptr<HeifPixelImage> const&, heif_encoder*, heif_encoding_options const&, heif_image_input_class) libheif/libheif/image-items/image_item.cc:388:50
#9 0x5556558f571e in HeifContext::encode_image(std::__1::shared_ptr<HeifPixelImage> const&, heif_encoder*, heif_encoding_options const&, heif_image_input_class) libheif/libheif/context.cc:1614:34
#10 0x55565567b324 in heif_context_encode_image libheif/libheif/api/libheif/heif_encoding.cc:711:39
#11 0x55565566e8ca in LLVMFuzzerTestOneInput libheif/fuzzing/encoder_fuzzer.cc:195:9
#12 0x5556555c59cd in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:619:13
#13 0x5556555b0742 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:329:6
#14 0x5556555b6610 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:865:9
#15 0x5556555e2142 in main /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerMain.cpp:20:10
#16 0x7c1b229ac082 in __libc_start_main /build/glibc-B3wQXB/glibc-2.31/csu/libc-start.c:308:16
#17 0x5556555a982d in _start
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /work/x265/source/encoder/frameencoder.cpp:201:9
BB Issue #1032
Original issue created by farindk (bitbucket username :Dirk Farin).
Created on Bitbucket: 2026-05-03
Last updated on Bitbucket: 2026-05-04
We got the following OSS-Fuzz report, indicating an undefined behavior in x265:
OSS-Fuzz link (may not yet be public): https://oss-fuzz.com/testcase-detail/6703023882829824