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 --- Misc/NEWS.d/next/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 Index: Python-3.12.13/Misc/NEWS.d/next/Security/2026-04-10-16-28-21.gh-issue-148395.kfzm0G.rst =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ Python-3.12.13/Misc/NEWS.d/next/Security/2026-04-10-16-28-21.gh-issue-148395.kfzm0G.rst 2026-04-24 23:01:53.772670857 +0200 @@ -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. Index: Python-3.12.13/Modules/_bz2module.c =================================================================== --- Python-3.12.13.orig/Modules/_bz2module.c 2026-03-03 13:39:30.000000000 +0100 +++ Python-3.12.13/Modules/_bz2module.c 2026-04-24 23:01:53.771388251 +0200 @@ -587,6 +587,7 @@ return result; error: + bzs->next_in = NULL; Py_XDECREF(result); return NULL; } Index: Python-3.12.13/Modules/_lzmamodule.c =================================================================== --- Python-3.12.13.orig/Modules/_lzmamodule.c 2026-03-03 13:39:30.000000000 +0100 +++ Python-3.12.13/Modules/_lzmamodule.c 2026-04-24 23:01:53.771598998 +0200 @@ -1114,6 +1114,7 @@ return result; error: + lzs->next_in = NULL; Py_XDECREF(result); return NULL; } Index: Python-3.12.13/Modules/zlibmodule.c =================================================================== --- Python-3.12.13.orig/Modules/zlibmodule.c 2026-03-03 13:39:30.000000000 +0100 +++ Python-3.12.13/Modules/zlibmodule.c 2026-04-24 23:01:53.771855952 +0200 @@ -1645,6 +1645,7 @@ return result; error: + self->zst.next_in = NULL; Py_XDECREF(result); return NULL; }