From fe18959c5d6bdb1bb504f46bf09bad302314fe87 Mon Sep 17 00:00:00 2001 From: Stan Ulbrych Date: Mon, 13 Apr 2026 02:14:54 +0100 Subject: [PATCH 1/2] 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) --- 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 + 3 files changed, 7 insertions(+) create mode 100644 Misc/NEWS.d/next/Security/2026-04-10-16-28-21.gh-issue-148395.kfzm0G.rst Index: Python-3.6.15/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-3.6.15/Misc/NEWS.d/next/Security/2026-04-10-16-28-21.gh-issue-148395.kfzm0G.rst 2026-04-24 23:13:16.485825630 +0200 @@ -0,0 +1,5 @@ +Fix a dangling input pointer in :class:`lzma.LZMADecompressor`, +: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. Index: Python-3.6.15/Modules/_bz2module.c =================================================================== --- Python-3.6.15.orig/Modules/_bz2module.c 2021-09-04 05:49:41.000000000 +0200 +++ Python-3.6.15/Modules/_bz2module.c 2026-04-24 23:13:16.486128721 +0200 @@ -587,6 +587,7 @@ return result; error: + bzs->next_in = NULL; Py_XDECREF(result); return NULL; } Index: Python-3.6.15/Modules/_lzmamodule.c =================================================================== --- Python-3.6.15.orig/Modules/_lzmamodule.c 2021-09-04 05:49:41.000000000 +0200 +++ Python-3.6.15/Modules/_lzmamodule.c 2026-04-24 23:13:16.486470586 +0200 @@ -1053,6 +1053,7 @@ return result; error: + lzs->next_in = NULL; Py_XDECREF(result); return NULL; }