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Fencer Vulns
medium 5.8

CVE-2026-31789 json

Heap Buffer Overflow in Hexadecimal Conversion

published 2026-04-07 7 mo ago modified 2026-08-13 2 mo ago also EUVD-2026-19968 , GHSA-j79m-9jxq-788r , JLSEC-2026-276

cvss
5.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 16%
public exploits
0
none known

Summary

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.

Patch / fix

  • julia AppBundler 1.0.1
  • julia OpenSSL_jll 3.0.20+0, 3.5.6+0
  • OpenSSL OpenSSL 3.0.20, 3.3.7, 3.4.5, 3.5.6, 3.6.2
  • Siemens SIMATIC CN 4100 V5.0
  • openssl Debian 12 3.0.19-1~deb12u2
  • openssl Debian 13 3.5.5-1~deb13u2
  • openssl Debian 14 3.6.2-1

debian advisories DEBIAN-CVE-2026-31789

  • openssl Ubuntu 22.04 LTS 3.0.2-0ubuntu1.23
  • openssl Ubuntu 24.04 LTS 3.0.13-0ubuntu3.9
  • openssl Ubuntu 25.10 3.5.3-1ubuntu3.3
  • openssl Ubuntu 26.10, Ubuntu 26.04 LTS 3.5.5-1ubuntu3
  • openssl-fips Ubuntu Pro FIPS-updates 24.04 LTS 3.0.13-0ubuntu3.12+Fips1

ubuntu advisories UBUNTU-CVE-2026-31789

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • openssl hummingbird 1 3.5.6-0.1.hum1
  • openssl-libs hummingbird 1 3.5.6-0.1.hum1
  • openssl-perl hummingbird 1 3.5.6-0.1.hum1
  • openssl-config-fips hummingbird 1 3.5.6-0.1.hum1
  • openssl-devel-engine hummingbird 1 3.5.6-0.1.hum1

red hat advisories RHSA-2026:7261

  • openssl-1_1 SLE Module for Legacy 15 SP7, SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 1.1.1w-150700.11.16.1
  • openssl-3 SLE Module for Basesystem 15 SP7 3.2.3-150700.5.31.1
  • openssl-3 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 3.5.0-160000.7.1
  • openssl-1_0_0 SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +7 more 1.0.2p-150000.3.105.1
  • openssl-1_1 SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE Micro 5.5 +2 more 1.1.1l-150500.17.51.1
  • openssl-1_1 SLES for SAP 15 SP4, SLES 15 SP4-LTSS, SLE Micro 5.4 +3 more 1.1.1l-150400.7.90.1
  • openssl-3 Linux Micro 6.0 3.1.4-12.1
  • openssl-3 Linux Micro 6.1 3.1.4-slfo.1.1_9.1

suse advisories SUSE-SU-2026:1577-1SUSE-SU-2026:1386-1SUSE-SU-2026:1375-1SUSE-SU-2026:21107-1SUSE-SU-2026:21186-1SUSE-SU-2026:1291-1

  • openssl-3 openSUSE Leap 16.0 3.5.0-160000.7.1
  • openssl-3 openSUSE Tumbleweed 3.5.3-4.1

opensuse advisories openSUSE-SU-2026:20525-1openSUSE-SU-2026:10533-1

  • openssl Alpine 3.21, Alpine 3.20 3.3.7-r0
  • openssl Alpine 3.24, Alpine 3.23, Alpine 3.22 3.5.6-r0

alpine advisories ALPINE-CVE-2026-31789

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • openssl Azure Linux 3.0 3.3.5-5

azure linux advisories AZL-81944

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-31789 updated cvss 5.8

openssl: OpenSSL: Heap buffer overflow on 32-bit systems from large X.509 certificate processing

  • Red Hat Enterprise Linux 6 openssl, openssl-perl Red Hat Enterprise Linux 7 ovmf, OVMF, AAVMF, openssl, openssl-libs, openssl-perl Red Hat Enterprise Linux 8 edk2, shim, openssl, shim-x64, edk2-ovmf, shim-aa64, +9 more Red Hat Enterprise Linux 9 edk2, shim, openssl, shim-x64, edk2-ovmf, shim-aa64, +7 more Red Hat Enterprise Linux 10 edk2, shim, openssl, shim-unsigned-x64, shim-unsigned-aarch64 Red Hat JBoss Core Services openssl
    +1 more products
    Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9
    affected: workaround, no fix available “Fix deferred”
  • Red Hat OpenShift AI (RHOAI) rhoai/odh-core-bff-rhel9, rhoai/odh-dashboard-rhel9, rhoai/odh-mod-arch-maas-rhel9, rhoai/odh-mod-arch-automl-rhel9, rhoai/odh-mod-arch-gen-ai-rhel9, rhoai/odh-mod-arch-mlflow-rhel9, +6 more
    under investigation
  • Red Hat Hardened Images openssl 3.5.6-0.1.hum1, openssl-libs 3.5.6-0.1.hum1, openssl-perl 3.5.6-0.1.hum1, openssl-config-fips 3.5.6-0.1.hum1, openssl-devel-engine 3.5.6-0.1.hum1
    fixed: vendor fix RHSA-2026:7261
  • Red Hat OpenShift AI (RHOAI) rhoai/odh-mlflow-rhel9, rhoai/odh-kube-rbac-proxy-rhel9, rhoai/odh-maas-controller-rhel9, rhoai/odh-mlflow-operator-rhel9, rhoai/odh-model-controller-rhel9, rhoai/odh-ogx-k8s-operator-rhel9, +14 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
7 mo ago

Exploit prediction

0.25% chance of exploitation in the next 30 days, higher than 16% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 5.8 CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:H
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA 3.1 5.8 CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:H
OSV 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
julia AppBundler
>=1.0.0, <1.0.1
1.0.1
julia OpenSSL_jll
>=3.0.8+0, <3.0.20+0
>=3.5.0+0, <3.5.6+0
3.0.20+0
3.5.6+0
julia Openresty_jll
>=1.27.1+0
 no fix listed

Affected products

  • OpenSSL OpenSSL
  • Siemens SIMATIC CN 4100

Classification

Weakness
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.