CVE-2026-19542 Stack-based out-of-bounds write in tdelete during tree rebalancing

What is CVE-2026-19542?

CVE-2026-19542 is a medium-severity memory corruption vulnerability in The GNU C Library glibc, published on 14 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Calling tdelete on a sufficiently deep tree in the GNU C Library version 2.1 to 2.44 may write one pointer past the end of an alloca-allocated array on the stack, which may crash the application.

The tdelete implementation keeps an explicit stack of parent nodes for rebalancing, which is grown as needed while descending the tree. Two rebalancing branches push an additional entry without checking the capacity, and write past the array when the stack is exactly full. Triggering this requires a node at a depth of exactly 40 (or 40 plus a multiple of 20), which implies a tree with at least a million nodes, so an attacker must drive a large number of insertions and deletions through an application that uses tsearch and tdelete. The written value is a pointer into a tree node and is not directly attacker controlled. No affected application in common distributions has been identified.

Weakness: CWE-121

Which versions are affected by CVE-2026-19542?

How do I fix CVE-2026-19542?

Apply the vendor's patch.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2026-19542 being exploited?

There is no known exploitation of CVE-2026-19542 in the wild and no public exploit code.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-100968, BELL-CVE-2026-19542, DEBIAN-CVE-2026-19542, ECHO-4020-d607-ea47, GHSA-hhcv-vc8h-vmrg, RHSA-2026:59721 and 1 more.