CVE-2026-31789 | Heap Buffer Overflow in Hexadecimal Conversion

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.

Published: 2026-04-07 Last update: 2026-05-12 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-31789 is rated Low Risk (39.6/100): CVSS Critical severity, with low exploitation likelihood (EPSS 0.01%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-31789

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-04-08 — 0.01% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-31789

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 [email protected]
5.8 3.1 MEDIUM
CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.0 4.7 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2026-31789

GitHub Security Advisory for CVE-2026-31789

GHSA-j79m-9jxq-788r · Severity: critical — Issue summary: Converting an excessively large OCTET STRING value to a hexadecimal string leads...

OS Trackers for CVE-2026-31789

vendor priority summary link
alpine — CVE-2026-31789: 1 source package rows (openssl); 5 state rows across 5 repos (3.20-main, 3.21-main, 3.22-main, 3.23-main, edge-main); fixed 5, open 0. https://security.alpinelinux.org/vuln/CVE-2026-31789
debian unimportant CVE-2026-31789 unimportant priority: Debian including 1 source packages (openssl), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2026-31789
redhat low — https://access.redhat.com/security/cve/CVE-2026-31789
suse high CVE-2026-31789 severity important: SUSE including 391 source package names (1.1.2-2.16:libopenssl3-3.2.3-150700.5.31.1, 1.1.2-2.16:openssl-3-3.2.3-150700.5.31.1, …), 732 product×package rows across 97 product lines (Container private-registry/harbor-core, Container private-registry/harbor-exporter, … (97 product lines)): Fixed 416, Known Affected 231, Known Not Affected 70, First Fixed 15. https://www.suse.com/security/cve/CVE-2026-31789/
ubuntu low CVE-2026-31789 low priority: Ubuntu including 5 source packages (edk2, nodejs, openssl, openssl-fips, openssl1.0), 37 status rows across 9 suites (bionic, focal, jammy, noble, questing, resolute, trusty, upstream, xenial): not-affected 17, DNE 8, released 5, needs-triage 4, needed 3. https://ubuntu.com/security/CVE-2026-31789

Affected software / configurations for CVE-2026-31789

Vendor Product Version Raw CPE
openssl openssl >= 3.0.0, < 3.0.20 cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*
openssl openssl >= 3.3.0, < 3.3.7 cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*
openssl openssl >= 3.4.0, < 3.4.5 cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*
openssl openssl >= 3.5.0, < 3.5.6 cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*
openssl openssl >= 3.6.0, < 3.6.2 cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*

References for CVE-2026-31789

cvelogic Threat Intelligence