CVE-2026-42790: Improper Certificate Validation vulnerability in Erlang OTP public_key (pubkey_cert and public_key modules) al

Routine

HIGH 8.1UPGRADE

CVE-2026-42790 is a high-severity flaw (CVSS 8.1) affecting erlang\/otp. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Improper Certificate Validation vulnerability in Erlang OTP public_key (pubkey_cert and public_key modules) allows a DNS nameConstraints bypass via subject CommonName fallback in TLS hostname verification. Two flaws combine to allow a subordinate CA whose DNS nameConstraints are restricted (e.g. permitted;DNS:allowed.example.com) to issue a leaf certificate that an OTP TLS client accepts as a valid identity for an out-of-scope hostname (e.g. vic

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	8.1 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.3% (top 72%)
CISA exploited list	No
Weakness	CWE-295, CWE-297
Published	2026-05-27
Last modified	2026-10-26

Publisher (CNA): EEF · Vendor: erlang

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-27 17:16 UTCPublished CVE record published
2026-10-26 11:10 UTCUpdated Record last modified

erlang erlang\/otp UPGRADE

Affected: >= 19.3 and < 26.2.5.21 · >= 27.0 and < 27.3.4.12 · >= 28.0 and < 28.5.0.1 · >= 29.0 and < 29.0.1

Fixed in: 26.2.5.21, 27.3.4.12, 28.5.0.1, 29.0.1

Safe to downgrade to: a release before 19.3

1. Check installed version

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

2. UPGRADE to 26.2.5.21 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade erlangotp

Note

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

3. If no update is available yet, DOWNGRADE to a release before 19.3 (Debian / Ubuntu)

apt-cache madison erlangotp sudo apt install erlangotp=<VERSION_BEFORE_19.3> sudo apt-mark hold erlangotp

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list erlangotp sudo dnf downgrade erlangotp-<VERSION_BEFORE_19.3> sudo dnf versionlock add erlangotp

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

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-2026-42790?

erlang\/otp: upgrade to 26.2.5.21, 27.3.4.12, 28.5.0.1, 29.0.1. Exact commands for each OS are on this page.

Is CVE-2026-42790 being exploited?

CVE-2026-42790 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-2026-42790 affect?

CVE-2026-42790 affects erlang\/otp. Severity is high (CVSS 8.1). Improper Certificate Validation vulnerability in Erlang OTP public_key (pubkey_cert and public_key modules) allows a DNS nameConstraints bypass via subject CommonName fallback in TLS hostname verification. Two flaws combine to allow a subo

How urgent is CVE-2026-42790?

Priority 35/100. High severity

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References

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