From e100aea7aded26a49abe96c3aae2d64ef195f397 Mon Sep 17 00:00:00 2001 From: Stan Ulbrych Date: Mon, 13 Apr 2026 02:14:54 +0100 Subject: [PATCH 1/3] gh-148395: Fix a possible UAF in `{LZMA,BZ2,_Zlib}Decompressor` (GH-148396) Fix dangling input pointer after `MemoryError` in _lzma/_bz2/_ZlibDecompressor.decompress (cherry picked from commit 8fc66aef6d7b3ae58f43f5c66f9366cc8cbbfcd2) Co-authored-by: Stan Ulbrych --- .../Security/2026-04-10-16-28-21.gh-issue-148395.kfzm0G.rst | 5 +++++ Modules/_bz2module.c | 1 + Modules/_lzmamodule.c | 1 + Modules/zlibmodule.c | 1 + 4 files changed, 8 insertions(+) create mode 100644 Misc/NEWS.d/next/Security/2026-04-10-16-28-21.gh-issue-148395.kfzm0G.rst diff --git a/Misc/NEWS.d/next/Security/2026-04-10-16-28-21.gh-issue-148395.kfzm0G.rst b/Misc/NEWS.d/next/Security/2026-04-10-16-28-21.gh-issue-148395.kfzm0G.rst new file mode 100644 index 00000000000000..9502189ab199c1 --- /dev/null +++ b/Misc/NEWS.d/next/Security/2026-04-10-16-28-21.gh-issue-148395.kfzm0G.rst @@ -0,0 +1,5 @@ +Fix a dangling input pointer in :class:`lzma.LZMADecompressor`, +:class:`bz2.BZ2Decompressor`, and internal :class:`!zlib._ZlibDecompressor` +when memory allocation fails with :exc:`MemoryError`, which could let a +subsequent :meth:`!decompress` call read or write through a stale pointer to +the already-released caller buffer. diff --git a/Modules/_bz2module.c b/Modules/_bz2module.c index 97bd44b4ac9694..a732e89d554448 100644 --- a/Modules/_bz2module.c +++ b/Modules/_bz2module.c @@ -587,6 +587,7 @@ decompress(BZ2Decompressor *d, char *data, size_t len, Py_ssize_t max_length) return result; error: + bzs->next_in = NULL; Py_XDECREF(result); return NULL; } diff --git a/Modules/_lzmamodule.c b/Modules/_lzmamodule.c index 7bbd6569aa2e44..103a6ef86c0d38 100644 --- a/Modules/_lzmamodule.c +++ b/Modules/_lzmamodule.c @@ -1114,6 +1114,7 @@ decompress(Decompressor *d, uint8_t *data, size_t len, Py_ssize_t max_length) return result; error: + lzs->next_in = NULL; Py_XDECREF(result); return NULL; } diff --git a/Modules/zlibmodule.c b/Modules/zlibmodule.c index f94c57e4c89c4f..9759593b6acff4 100644 --- a/Modules/zlibmodule.c +++ b/Modules/zlibmodule.c @@ -1645,6 +1645,7 @@ decompress(ZlibDecompressor *self, uint8_t *data, return result; error: + self->zst.next_in = NULL; Py_XDECREF(result); return NULL; } From 287992c12328141105ef29ee70f136ee42feb83c Mon Sep 17 00:00:00 2001 From: Stan Ulbrych Date: Mon, 13 Apr 2026 17:22:05 +0100 Subject: [PATCH 2/3] remove _ZlibDecompressor --- .../Security/2026-04-10-16-28-21.gh-issue-148395.kfzm0G.rst | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/Misc/NEWS.d/next/Security/2026-04-10-16-28-21.gh-issue-148395.kfzm0G.rst b/Misc/NEWS.d/next/Security/2026-04-10-16-28-21.gh-issue-148395.kfzm0G.rst index 9502189ab199c1..349d1cf3cacdf4 100644 --- a/Misc/NEWS.d/next/Security/2026-04-10-16-28-21.gh-issue-148395.kfzm0G.rst +++ b/Misc/NEWS.d/next/Security/2026-04-10-16-28-21.gh-issue-148395.kfzm0G.rst @@ -1,5 +1,5 @@ Fix a dangling input pointer in :class:`lzma.LZMADecompressor`, -:class:`bz2.BZ2Decompressor`, and internal :class:`!zlib._ZlibDecompressor` +and :class:`bz2.BZ2Decompressor` when memory allocation fails with :exc:`MemoryError`, which could let a subsequent :meth:`!decompress` call read or write through a stale pointer to the already-released caller buffer. From 700cb059d70fad66cfeec2230f3f111ac9cafda4 Mon Sep 17 00:00:00 2001 From: Stan Ulbrych Date: Mon, 13 Apr 2026 17:23:47 +0100 Subject: [PATCH 3/3] revert that --- .../Security/2026-04-10-16-28-21.gh-issue-148395.kfzm0G.rst | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/Misc/NEWS.d/next/Security/2026-04-10-16-28-21.gh-issue-148395.kfzm0G.rst b/Misc/NEWS.d/next/Security/2026-04-10-16-28-21.gh-issue-148395.kfzm0G.rst index 349d1cf3cacdf4..9502189ab199c1 100644 --- a/Misc/NEWS.d/next/Security/2026-04-10-16-28-21.gh-issue-148395.kfzm0G.rst +++ b/Misc/NEWS.d/next/Security/2026-04-10-16-28-21.gh-issue-148395.kfzm0G.rst @@ -1,5 +1,5 @@ Fix a dangling input pointer in :class:`lzma.LZMADecompressor`, -and :class:`bz2.BZ2Decompressor` +:class:`bz2.BZ2Decompressor`, and internal :class:`!zlib._ZlibDecompressor` when memory allocation fails with :exc:`MemoryError`, which could let a subsequent :meth:`!decompress` call read or write through a stale pointer to the already-released caller buffer.