CVE-2026-31789: Issue summary: Converting an excessively large OCTET STRING value to a hexadecimal string leads to a heap buff

Q: How do I fix CVE-2026-31789?

openssl: upgrade to 3.0.20, 3.3.7, 3.4.5, 3.5.6, 3.6.2. Exact commands for each OS are on this page.

Q: Is CVE-2026-31789 being exploited?

CVE-2026-31789 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-31789 affect?

CVE-2026-31789 affects openssl. Severity is critical (CVSS 9.8). 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 co

Q: How urgent is CVE-2026-31789?

Priority 48/100. Critical severity; Remotely exploitable, no login, no user action; On your watchlist

This month

CRITICAL 9.8REMOTEWATCHLISTUPGRADE

CVE-2026-31789 is a critical-severity flaw (CVSS 9.8) affecting openssl. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

Critical severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 85%)
CISA exploited list	No
Weakness	CWE-787
Published	2026-04-07
Last modified	2026-07-24

Publisher (CNA): OpenSSL Software Foundation · Vendor: openssl

Last updated 2026-07-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-07 22:16 UTCPublished CVE record published
2026-07-24 23:10 UTCUpdated Record last modified

openssl openssl UPGRADE

Affected: >= 3.0.0 and < 3.0.20 · >= 3.3.0 and < 3.3.7 · >= 3.4.0 and < 3.4.5 · >= 3.5.0 and < 3.5.6 · >= 3.6.0 and < 3.6.2

Fixed in: 3.0.20, 3.3.7, 3.4.5, 3.5.6, 3.6.2

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy openssl || rpm -q openssl || openssl --version

2. UPGRADE to 3.0.20 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade openssl

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade openssl

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-31789?

openssl: upgrade to 3.0.20, 3.3.7, 3.4.5, 3.5.6, 3.6.2. Exact commands for each OS are on this page.

Is CVE-2026-31789 being exploited?

CVE-2026-31789 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-31789 affect?

CVE-2026-31789 affects openssl. Severity is critical (CVSS 9.8). 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 co

How urgent is CVE-2026-31789?

Priority 48/100. Critical severity; Remotely exploitable, no login, no user action; On your watchlist

Software pages

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References

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