Heap Buffer Overflow in Hexadecimal Conversion

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Summary

CVECVE-2026-31789
StatePUBLISHED
Assigneropenssl
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-07 22:16:21 UTC
Updated2026-04-08 21:27:00 UTC
DescriptionIssue 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

EPSS: 0.000110000 probability, percentile 0.012060000 (date 2026-04-09)

Problem Types: CWE-787 | CWE-787 CWE-787 Out-of-bounds Write

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
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

ReferenceSourceLinkTags
openssl-library.org/news/secadv/20260407.txt [email protected] openssl-library.org
github.com/openssl/openssl/commit/7a9087efd769f362ad9c0e30c7baaa6bbfa65ecf [email protected] github.com
github.com/openssl/openssl/commit/364f095b80601db632b0def6a33316967f863bde [email protected] github.com
github.com/openssl/openssl/commit/945b935ac66cc7f1a41f1b849c7c25adb5351f49 [email protected] github.com
github.com/openssl/openssl/commit/a24216018e1ede8ff01a4ff5afff7dfbd443e2f9 [email protected] github.com
github.com/openssl/openssl/commit/a91e537d16d74050dbde50bb0dfb1fe9930f0521 [email protected] github.com
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)

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