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

Affected: The GNU C Library glibc

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.

USN-8737-1 — glibc vulnerabilities

Affected: Ubuntu:22.04:LTS: glibc, Ubuntu:26.04:LTS: glibc

It was discovered that GNU C Library had a buffer overflow in the strfmon function when handling right-justification padding. An attacker could possibly use this issue to cause a denial of service or execute arbitrary code. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-19499)

It was discovered that GNU C Library had an out-of-bounds stack array access in the tdelete function. An attacker could possibly use this issue to cause a denial of service or execute arbitrary code. (CVE-2026-19542)

It was discovered that GNU C Library incorrectly handled memory when calling wordexp with the WRDE_APPEND flag. An attacker could possibly use this issue to cause a denial of service. (CVE-2026-6368)

It was discovered that GNU C Library had a stack overflow in the wordexp function when expanding paths beginning with a tilde followed by a long username. An attacker could possibly use this issue to cause a denial of service or execute arbitrary code. (CVE-2026-6791)

It was discovered that GNU C Library had a hang in the SHIFT_JISX0213 character set converter. An attacker could possibly use this issue to cause a denial of service. (CVE-2026-77117)

It was discovered that GNU C Library had a hang in the EUC_JISX0213 character set converter. An attacker could possibly use this issue to cause a denial of service. (CVE-2026-80489)

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

USN-8737-1 — glibc vulnerabilities