Heap Buffer Overflow in Hexadecimal Conversion
Summary
| CVE | CVE-2026-31789 |
|---|---|
| State | PUBLISHED |
| Assigner | openssl |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-04-07 22:16:21 UTC |
| Updated | 2026-04-23 15:39:34 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 9.8 CRITICAL from [email protected]
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS: 0.000120000 probability, percentile 0.015540000 (date 2026-04-14)
Problem Types: CWE-787 | CWE-787 CWE-787 Out-of-bounds Write
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
NoneUser Interaction
NoneScope
UnchangedConfidentiality
HighIntegrity
HighAvailability
HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD Known Affected Configurations (CPE 2.3)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | OpenSSL | OpenSSL | affected 3.6.0 3.6.2 semver | Not specified |
| CNA | OpenSSL | OpenSSL | affected 3.5.0 3.5.6 semver | Not specified |
| CNA | OpenSSL | OpenSSL | affected 3.4.0 3.4.5 semver | Not specified |
| CNA | OpenSSL | OpenSSL | affected 3.3.0 3.3.7 semver | Not specified |
| CNA | OpenSSL | OpenSSL | affected 3.0.0 3.0.20 semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| openssl-library.org/news/secadv/20260407.txt | [email protected] | openssl-library.org | Vendor Advisory |
| github.com/openssl/openssl/commit/7a9087efd769f362ad9c0e30c7baaa6bbfa65ecf | [email protected] | github.com | Patch |
| github.com/openssl/openssl/commit/364f095b80601db632b0def6a33316967f863bde | [email protected] | github.com | Patch |
| github.com/openssl/openssl/commit/945b935ac66cc7f1a41f1b849c7c25adb5351f49 | [email protected] | github.com | Patch |
| github.com/openssl/openssl/commit/a24216018e1ede8ff01a4ff5afff7dfbd443e2f9 | [email protected] | github.com | Patch |
| github.com/openssl/openssl/commit/a91e537d16d74050dbde50bb0dfb1fe9930f0521 | [email protected] | github.com | Patch |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Quoc Tran (Xint.io - US Team) (en)
CNA: Igor Ustinov (en)
There are currently no legacy QID mappings associated with this CVE.