CVE-2026-31789
Heap Buffer Overflow in Hexadecimal Conversion
Description
Issue summary: Converting an excessively large OCTET STRING value to a hexadecimal string leads to a heap buffer overflow on 32 bit platforms. Impact summary: A heap buffer overflow may lead to a crash or possibly an attacker controlled code execution or other undefined behavior. If an attacker can supply a crafted X.509 certificate with an excessively large OCTET STRING value in extensions such as the Subject Key Identifier (SKID) or Authority Key Identifier (AKID) which are being converted to hex, the size of the buffer needed for the result is calculated as multiplication of the input length by 3. On 32 bit platforms, this multiplication may overflow resulting in the allocation of a smaller buffer and a heap buffer overflow. Applications and services that print or log contents of untrusted X.509 certificates are vulnerable to this issue. As the certificates would have to have sizes of over 1 Gigabyte, printing or logging such certificates is a fairly unlikely operation and only 32 bit platforms are affected, this issue was assigned Low severity. The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.
INFO
Published Date :
April 7, 2026, 10:16 p.m.
Last Modified :
April 23, 2026, 3:39 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | CRITICAL | [email protected] |
Solution
- Update affected software to a patched version.
- Avoid logging or printing large X.509 certificates.
- Use 64-bit platforms where possible.
Public PoC/Exploit Available at Github
CVE-2026-31789 has a 3 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-31789.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-31789 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-31789
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
None
trivy-nginx-scan
All Public RunWhen Helm Charts - Managed by terraform
Shell Dockerfile Go Template
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-31789 vulnerability anywhere in the article.
-
TheCyberThrone
OpenSSL 3.6.2: The Moderate Severity Wave
OpenSSL 3.6.2 landed this week carrying eight CVE fixes, with the project rating the most severe issue as Moderate. On the surface, that sounds reassuring—no critical exploits, no ransomware-grade zer ... Read more
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CybersecurityNews
Multiple OpenSSL Vulnerabilities Exposes Sensitive Data in RSA KEM Handling
OpenSSL has released a broad April 2026 security update that fixes seven vulnerabilities across supported branches, led by CVE-2026-31790, a moderate-severity flaw in RSA KEM RSASVE encapsulation that ... Read more
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Help Net Security
OpenSSL 3.6.2 lands with eight CVE fixes
OpenSSL 3.6.2 patches eight CVEs across a range of components. The project rates the most severe issue in the release as Moderate. What got fixed The release fixes incorrect failure handling in RSA KE ... Read more
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Daily CyberSecurity
OpenSSL Issues Major Security Advisory: RSA and Memory Vulnerabilities Fixed
OpenSSL has released a comprehensive security advisory detailing seven vulnerabilities ranging from Moderate to Low severity. The report, dated April 7, 2026, highlights critical fixes for modern vers ... Read more
The following table lists the changes that have been made to the
CVE-2026-31789 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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Initial Analysis by [email protected]
Apr. 23, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Added CPE Configuration OR *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.0.0 up to (excluding) 3.0.20 *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.3.0 up to (excluding) 3.3.7 *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.4.0 up to (excluding) 3.4.5 *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.5.0 up to (excluding) 3.5.6 *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.6.0 up to (excluding) 3.6.2 Added Reference Type OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/364f095b80601db632b0def6a33316967f863bde Types: Patch Added Reference Type OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/7a9087efd769f362ad9c0e30c7baaa6bbfa65ecf Types: Patch Added Reference Type OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/945b935ac66cc7f1a41f1b849c7c25adb5351f49 Types: Patch Added Reference Type OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/a24216018e1ede8ff01a4ff5afff7dfbd443e2f9 Types: Patch Added Reference Type OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/a91e537d16d74050dbde50bb0dfb1fe9930f0521 Types: Patch Added Reference Type OpenSSL Software Foundation: https://openssl-library.org/news/secadv/20260407.txt Types: Vendor Advisory -
New CVE Received by [email protected]
Apr. 07, 2026
Action Type Old Value New Value Added Description Issue summary: Converting an excessively large OCTET STRING value to a hexadecimal string leads to a heap buffer overflow on 32 bit platforms. Impact summary: A heap buffer overflow may lead to a crash or possibly an attacker controlled code execution or other undefined behavior. If an attacker can supply a crafted X.509 certificate with an excessively large OCTET STRING value in extensions such as the Subject Key Identifier (SKID) or Authority Key Identifier (AKID) which are being converted to hex, the size of the buffer needed for the result is calculated as multiplication of the input length by 3. On 32 bit platforms, this multiplication may overflow resulting in the allocation of a smaller buffer and a heap buffer overflow. Applications and services that print or log contents of untrusted X.509 certificates are vulnerable to this issue. As the certificates would have to have sizes of over 1 Gigabyte, printing or logging such certificates is a fairly unlikely operation and only 32 bit platforms are affected, this issue was assigned Low severity. The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary. Added CWE CWE-787 Added Reference https://github.com/openssl/openssl/commit/364f095b80601db632b0def6a33316967f863bde Added Reference https://github.com/openssl/openssl/commit/7a9087efd769f362ad9c0e30c7baaa6bbfa65ecf Added Reference https://github.com/openssl/openssl/commit/945b935ac66cc7f1a41f1b849c7c25adb5351f49 Added Reference https://github.com/openssl/openssl/commit/a24216018e1ede8ff01a4ff5afff7dfbd443e2f9 Added Reference https://github.com/openssl/openssl/commit/a91e537d16d74050dbde50bb0dfb1fe9930f0521 Added Reference https://openssl-library.org/news/secadv/20260407.txt