CVE-2026-7383 — Possible Heap Buffer Overflow in ASN.1 Multibyte String Conversion

Affected: OpenSSL

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 input length; no network protocol or certificate-handling path in OpenSSL exercises the overflow. Triggering the bug requires an application that calls ASN1_mbstring_copy() or ASN1_mbstring_ncopy() directly, or registers a custom string type via ASN1_STRING_TABLE_add(), with attacker-controlled input on the order of half a gigabyte or more. For these reasons this issue was assigned Low severity.

The FIPS modules in 4.0, 3.6, 3.5, 3.4 and 3.0 are not affected by this issue, as the affected code is…

USN-8414-1 — openssl vulnerabilities

Affected: Ubuntu:22.04:LTS: openssl, Ubuntu:24.04:LTS: openssl, Ubuntu:25.10: openssl, Ubuntu:26.04:LTS: openssl

Frank Buss discovered that OpenSSL had a heap buffer over-read in ASN.1 content parsing. An attacker could possibly use this issue to cause OpenSSL to crash, resulting in a denial of service, or obtain sensitive information. (CVE-2026-34180)

Pavol Zacik and Alex Gaynor discovered that OpenSSL incorrectly accepted PKCS#12 files with short HMAC keys when using PBMAC1. An attacker could possibly use this issue to bypass integrity checks. This issue only affected Ubuntu 25.10 and Ubuntu 26.04 LTS. (CVE-2026-34181)

Asim Viladi Oglu Manizada and Alex Gaynor discovered that OpenSSL could accept forged CMS AuthEnvelopedData messages. An attacker could possibly use this issue to bypass message authentication checks. (CVE-2026-34182)

Abhinav Agarwal discovered that OpenSSL had unbounded memory growth in the QUIC PATH_CHALLENGE handler. A remote attacker could possibly use this issue to cause OpenSSL to use excessive resources, leading to a denial of service. This issue only affected Ubuntu 25.10 and Ubuntu 26.04 LTS. (CVE-2026-34183)

Sunwoo Lee, Hyuk Lim, and Seunghyun Yoon discovered that OpenSSL had a NULL pointer dereference in QUIC server initial packet handling. A remote attacker could possibly use this issue to cause OpenSSL to crash, resulting in a denial of service. This issue only affected Ubuntu 25.10 and Ubuntu 26.04 LTS. (CVE-2026-42764)

Mayank Jangid, Kushal Khemka, Hari Priandana, Bhabani Sankar Das, and Qifan Zhang discovered that OpenSSL had a possible NULL derefe…

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CVE-2026-7383 — Possible Heap Buffer Overflow in ASN.1 Multibyte String Conversion

USN-8414-1 — openssl vulnerabilities