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🛡️ CVE-2026-7383 — openssl

🟠 CVSS 8.1 — High ✅ No Known Exploit CWE-787 NVD
8.1
CVSS Score
0 Low4 Medium7 High9 Critical10

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 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 outside the OpenSSL FIPS module

boundary.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: High — the attacker first has to win a race, learn a secret or otherwise prepare the target.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: High — total loss, or loss the attacker controls.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: High — total loss, or loss the attacker controls.

Weakness class

CVE-2026-7383 is classified as CWE-787: Out-of-bounds Write. Data is written past the end or before the start of a buffer, corrupting whatever is stored there.

Affected software

CVE-2026-7383 is recorded against 1 package.

  • openssl

Timeline and source

Published on 9 June 2026 and last revised on 23 July 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com
github.com
github.com
github.com
github.com
openssl-library.org

Other advisories for this package

openssl has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-787: Out-of-bounds Write) in other software:

CVE-2026-7383 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity HIGH
CVSS Score 8.1
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE CWE-787
Public Exploit ✅ No
Source NVD
Published 2026-06-09
Updated 2026-08-20
Modified 2026-07-23

Affected Packages

Software From version Fixed in
openssl — —

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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