Low [CVE-2026-16517] Signed Integer Overflow in archive_write_zip_header

A signed integer overflow vulnerability was found in libarchive's ZIP writer. In the archive_write_zip_header function in archive_write_set_format_zip.c, when ZIP encryption is enabled and the entry file size is close to INT64_MAX, the addition of the encryption overhead to the entry size overflows int64_t, resulting in undefined behavior.

This could lead to incorrect Zip64 extension decisions or potential memory corruption. Red Hat Product Security rates this issue as Low severity.

The vulnerability is in the ZIP write path only and requires both ZIP encryption to be enabled and a file size near INT64_MAX, making real-world exploitation highly unlikely. The resulting undefined behavior could theoretically cause incorrect Zip64 extension decisions or a crash, but the conditions are too contrived for practical exploitation.

Weakness: CWE-190. Affected Red Hat products: Red Hat Hardened Images; Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat OpenShift Container Platform 4.

Red Hat lists Red Hat Enterprise Linux 9 as not affected. Red Hat fixing advisory: RHSA-2026:43818.

Affected products named by the advisory: Red Hat package: libarchive.