From: Stan Ulbrych <stan@python.org>
Date: Mon, 13 Apr 2026 21:42:24 +0000 (+0100)
Subject: [3.10] gh-148395: Fix a possible UAF in `{LZMA,BZ2}Decompressor` (GH-148396) (#148505)
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=47128e64f98c3a20271138a98c2922bea2a3ee0e;p=thirdparty%2FPython%2Fcpython.git

[3.10] gh-148395: Fix a possible UAF in `{LZMA,BZ2}Decompressor` (GH-148396) (#148505)

Fix dangling input pointer after `MemoryError` in _lzma/_bz2/_ZlibDecompressor.decompress

(cherry picked from commit 8fc66aef6d7b3ae58f43f5c66f9366cc8cbbfcd2)
---

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 000000000000..b095329bd913
--- /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`
+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 798e9efc628f..b08ac5e44e52 100644
--- a/Modules/_bz2module.c
+++ b/Modules/_bz2module.c
@@ -595,6 +595,7 @@ 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 915c0c918f64..52087c38cb22 100644
--- a/Modules/_lzmamodule.c
+++ b/Modules/_lzmamodule.c
@@ -1102,6 +1102,7 @@ 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;
 }