From 5b8d2401cff29da8a3bfc6c390b03c31a7efc843 Mon Sep 17 00:00:00 2001 From: Stan Ulbrych Date: Mon, 13 Apr 2026 02:14:54 +0100 Subject: [PATCH] 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 661847ad26702e..6c83ad3fa33d3d 100644 --- a/Modules/_bz2module.c +++ b/Modules/_bz2module.c @@ -589,6 +589,7 @@ 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 97f3a8f03da9a8..8d22ad318dabd1 100644 --- a/Modules/_lzmamodule.c +++ b/Modules/_lzmamodule.c @@ -1112,6 +1112,7 @@ 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 f59f9a76abd5ea..2b7def45cae476 100644 --- a/Modules/zlibmodule.c +++ b/Modules/zlibmodule.c @@ -1675,6 +1675,7 @@ decompress(ZlibDecompressor *self, uint8_t *data, return result; error: + self->zst.next_in = NULL; Py_XDECREF(result); return NULL; }