CVE-2026-7383

Technical Description

Issue summary: A signed integer overflow when sizing the destination

buffer for Unicode output in ASN1_mbstring_ncopy() can lead to a heap

buffer overflow.

Impact summary: A heap buffer overflow may lead to a crash or possibly

attacker controlled code execution or other undefined behaviour.

In ASN1_mbstring_copy() and ASN1_mbstring_ncopy() the destination

size for Unicode output is computed in a signed int: by left shift

of the input character count for BMPSTRING (UTF-16) and

UNIVERSALSTRING (UTF-32), and by summing per-character byte counts

for UTF8STRING. The calculation overflows when the input reaches

around 2^30 characters. In the worst case (UNIVERSALSTRING at 2^30

characters) the size wraps to zero, OPENSSL_malloc(1) is called, and

the subsequent character copy writes several gigabytes past the

one-byte allocation.

X.509 certificate processing routes through ASN1_STRING_set_by_NID(),

whose DIRSTRING_TYPE mask excludes UNIVERSALSTRING and whose per-NID

size limits cap the inpu

Remediation

Check the references section for vendor advisories and patches from openssl. Update openssl to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected Products

References