new file mode 100644
@@ -0,0 +1,68 @@
+From ae7abca7c721c73bb4aadf41a82a720a842a4364 Mon Sep 17 00:00:00 2001
+From: Lasse Collin <lasse.collin@tukaani.org>
+Date: Sun, 29 Mar 2026 19:11:21 +0300
+Subject: [PATCH] liblzma: Fix a buffer overflow in lzma_index_append()
+
+If lzma_index_decoder() was used to decode an Index that contained no
+Records, the resulting lzma_index had an invalid internal "prealloc"
+value. If lzma_index_append() was called on this lzma_index, too
+little memory would be allocated and a buffer overflow would occur.
+
+While this combination of the API functions is meant to work, in the
+real-world apps this call sequence is rare or might not exist at all.
+
+This bug is older than xz 5.0.0, so all stable releases are affected.
+
+CVE: CVE-2026-34743
+Upstream-Status: Backport [https://github.com/tukaani-project/xz/commit/8538443d08591693a8c61f3a03656650f39c7c32]
+
+Reported-by: GitHub user christos-spearbit
+(cherry picked from commit c8c22869e780ff57c96b46939c3d79ff99395f87)
+(cherry picked from commit 8538443d08591693a8c61f3a03656650f39c7c32)
+Signed-off-by: Hugo SIMELIERE (Schneider Electric) <hsimeliere.opensource@witekio.com>
+---
+ src/liblzma/common/index.c | 21 +++++++++++++++++++++
+ 1 file changed, 21 insertions(+)
+
+diff --git a/src/liblzma/common/index.c b/src/liblzma/common/index.c
+index 8a35f439..dae7cab5 100644
+--- a/src/liblzma/common/index.c
++++ b/src/liblzma/common/index.c
+@@ -434,6 +434,26 @@ lzma_index_prealloc(lzma_index *i, lzma_vli records)
+ if (records > PREALLOC_MAX)
+ records = PREALLOC_MAX;
+
++ // If index_decoder.c calls us with records == 0, it's decoding
++ // an Index that has no Records. In that case the decoder won't call
++ // lzma_index_append() at all, and i->prealloc isn't used during
++ // the Index decoding either.
++ //
++ // Normally the first lzma_index_append() call from the Index decoder
++ // would reset i->prealloc to INDEX_GROUP_SIZE. With no Records,
++ // lzma_index_append() isn't called and the resetting of prealloc
++ // won't occur either. Thus, if records == 0, use the default value
++ // INDEX_GROUP_SIZE instead.
++ //
++ // NOTE: lzma_index_append() assumes i->prealloc > 0. liblzma <= 5.8.2
++ // didn't have this check and could set i->prealloc = 0, which would
++ // result in a buffer overflow if the application called
++ // lzma_index_append() after decoding an empty Index. Appending
++ // Records after decoding an Index is a rare thing to do, but
++ // it is supposed to work.
++ if (records == 0)
++ records = INDEX_GROUP_SIZE;
++
+ i->prealloc = (size_t)(records);
+ return;
+ }
+@@ -686,6 +706,7 @@ lzma_index_append(lzma_index *i, const lzma_allocator *allocator,
+ ++g->last;
+ } else {
+ // We need to allocate a new group.
++ assert(i->prealloc > 0);
+ g = lzma_alloc(sizeof(index_group)
+ + i->prealloc * sizeof(index_record),
+ allocator);
+--
+2.43.0
+
@@ -30,6 +30,7 @@ SRC_URI = "https://github.com/tukaani-project/xz/releases/download/v${PV}/xz-${P
file://CVE-2025-31115-02.patch \
file://CVE-2025-31115-03.patch \
file://CVE-2025-31115-04.patch \
+ file://CVE-2026-34743.patch \
"
SRC_URI[sha256sum] = "8db6664c48ca07908b92baedcfe7f3ba23f49ef2476864518ab5db6723836e71"
UPSTREAM_CHECK_REGEX = "releases/tag/v(?P<pver>\d+(\.\d+)+)"