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{"schema_version":"1.9.0","id":"GHSA-3h9h-qfvw-98hq","published":"2026-04-06T17:51:11Z","modified":"2026-07-13T16:43:02.056352689Z","aliases":["CVE-2025-64181","PYSEC-2026-2843"],"summary":"OpenEXR Makes Use of Uninitialized Memory","details":"### Summary\nWhile fuzzing `openexr_exrcheck_fuzzer`, Valgrind reports a conditional branch depending on uninitialized data inside `generic_unpack`. This indicates a use of uninitialized memory (CWE-457). The issue is reproducible with the current OSS-Fuzz harness and a single-file PoC.\n\n### Details\n\n**Environment:**\n- Tooling: `valgrind --tool=memcheck --track-origins=yes`\n- Target: `openexr_exrcheck_fuzzer`\n- OS: Ubuntu 20.04.6 LTS focal x86_64\n- openexr version and Git-commit hash: ` openexr 3.4.2 | commit fd657e8a41e157e5841c7cc2e2a5efe094b069a1 (grafted, HEAD -> main, origin/main, origin/HEAD)`\n\nFunction: `generic_unpack`\n\nPossible root cause (based on observed symptoms):\nThe unpacker is branching on bytes in a scratch buffer that were never written because the decode step didn’t fully populate it.\n- The first use flagged is in `generic_unpack()`. That function reads from the decompressed/expanded pixel buffer to scatter data into the framebuffer. A “conditional jump depends on uninitialised value(s)” means it’s consulting bytes in that buffer before they were written.\n- Valgrind says the uninitialised value “was created by a heap allocation (malloc)”, not the stack: this matches a per-tile/per-scanline decode scratch buffer allocated in `exr_decoding_run()`.\n\n**Valgrind Trace (top frames):**\n```bash\n==454== Conditional jump or move depends on uninitialised value(s)\n==454== at 0x4539BE: generic_unpack (in /out/openexr_exrcheck_fuzzer)\n==454== by 0x44B85F: exr_decoding_run (in /out/openexr_exrcheck_fuzzer)\n==454== by 0x38BC5F: Imf_4_0::(anonymous namespace)::TileProcess::run_decode(_priv_exr_context_t const*, int, Imf_4_0::FrameBuffer const*, std::__1::vector<Imf_4_0::Slice, std::__1::allocator<Imf_4_0::Slice> > const&) (in /out/openexr_exrcheck_fuzzer)\n==454== by 0x388BE1: Imf_4_0::TiledInputFile::Data::readTiles(int, int, int, int, int, int) (in /out/openexr_exrcheck_fuzzer)\n==454== by 0x388619: Imf_4_0::TiledInputFile::readTiles(int, int, int, int, int, int) (in /out/openexr_exrcheck_fuzzer)\n==454== by 0x353755: Imf_4_0::InputFile::Data::bufferedReadPixels(int, int) (in /out/openexr_exrcheck_fuzzer)\n==454== by 0x352286: Imf_4_0::InputFile::readPixels(int) (in /out/openexr_exrcheck_fuzzer)\n==454== by 0x3190FA: Imf_4_0::(anonymous namespace)::readMultiPart(Imf_4_0::MultiPartInputFile&, bool, bool) (in /out/openexr_exrcheck_fuzzer)\n==454== by 0x314C4D: Imf_4_0::checkOpenEXRFile(char const*, unsigned long, bool, bool, bool) (in /out/openexr_exrcheck_fuzzer)\n==454== Uninitialised value was created by a heap allocation at 0x483B7F3: malloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)\n```\n\n### PoC\nIn the attached archive, you will find:\n- The executable used for our tests.\n- The testcase used to trigger the bug.\n\nTo observe the bug, simply run the OSS-Fuzz helper script:\n```bash\ngit clone https://github.com/google/oss-fuzz.git\ncd oss-fuzz\n\npython3 infra/helper.py build_image openexr\npython3 infra/helper.py build_fuzzers --sanitizer=none openexr\npython3 infra/helper.py shell openexr\n\napt update && apt install -y valgrind\nulimit -n 65535\nvalgrind --tool=memcheck --track-origins=yes /out/openexr_exrcheck_fuzzer /path/to/poc\n```\n\n### Impact\n- Undefined Behavior\n- Potential crash\n- Denial of Service\n\n**Credit:** Aldo Ristori\n[archive0.zip](https://github.com/user-attachments/files/23024726/archive0.zip)\n\n\n\n### Update Note:\nOther saved testcases from the fuzzing campaign trigger the same underlying bug, but with a different manifestation. So there is one root cause (missing post-decode validation / zero-init before any unpack), with different call-sites. Below there are several archives, formatted like the previous one, that reproduce the other test cases.\n\n**Other observed sinks (distinct manifestations of the same bug):**\n\n**Deep pointers path:**\ngeneric_unpack_deep_pointers (deep scanline/tiled)\n[archive1.zip](https://github.com/user-attachments/files/23024736/archive1.zip)\n\n\n**Deep sample table path:**\nunpack_sample_table (deep scanline)\n[archive2.zip](https://github.com/user-attachments/files/23024740/archive2.zip)\n\n\n**Half conversion path:**\nhalf_to_float_buffer_f16c via unpack_half_to_float_3chan_planar\n[archive3.zip](https://github.com/user-attachments/files/23024744/archive3.zip)\n\n\n**Deep compositing:**\nCompositeDeepScanLine::readPixels → ThreadPool::addTask → LineCompositeTask::execute\n[archive4.zip](https://github.com/user-attachments/files/23024746/archive4.zip)","affected":[{"package":{"name":"openexr","ecosystem":"PyPI","purl":"pkg:pypi/openexr"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.3.0"},{"fixed":"3.3.6"}]}],"versions":["3.3.0","3.3.1","3.3.2","3.3.3","3.3.4","3.3.5"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-3h9h-qfvw-98hq/GHSA-3h9h-qfvw-98hq.json"}},{"package":{"name":"openexr","ecosystem":"PyPI","purl":"pkg:pypi/openexr"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.4.0"},{"fixed":"3.4.3"}]}],"versions":["3.4.0","3.4.1","3.4.2"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-3h9h-qfvw-98hq/GHSA-3h9h-qfvw-98hq.json"}}],"references":[{"type":"WEB","url":"https://github.com/AcademySoftwareFoundation/openexr/security/advisories/GHSA-3h9h-qfvw-98hq"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-64181"},{"type":"PACKAGE","url":"https://github.com/AcademySoftwareFoundation/openexr"},{"type":"WEB","url":"https://github.com/user-attachments/files/23024726/archive0.zip"},{"type":"WEB","url":"https://github.com/user-attachments/files/23024736/archive1.zip"},{"type":"WEB","url":"https://github.com/user-attachments/files/23024740/archive2.zip"},{"type":"WEB","url":"https://github.com/user-attachments/files/23024744/archive3.zip"},{"type":"WEB","url":"https://github.com/user-attachments/files/23024746/archive4.zip"}],"database_specific":{"cwe_ids":["CWE-457"],"github_reviewed":true,"github_reviewed_at":"2026-04-06T17:51:11Z","nvd_published_at":"2025-11-10T22:15:36Z","severity":"LOW"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"type":"CVSS_V4","score":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P"}]} |