CVE-2026-79772: Nokogiri versions before 1.19.1 fail to check the return value from xmlC14NExecute in the canonicalize method,

Routine

MEDIUM 5.3REMOTEUPGRADE

CVE-2026-79772 is a medium-severity flaw (CVSS 5.3) affecting nokogiri. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Nokogiri versions before 1.19.1 fail to check the return value from xmlC14NExecute in the canonicalize method, returning an empty string on failure instead of raising an exception. Attackers can exploit this to bypass signature validation in downstream SAML libraries by providing invalid canonicalized XML that is incorrectly accepted as valid.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 73%)
CISA exploited list	No
Weakness	CWE-252
Published	2026-08-25
Last modified	2026-09-01

Publisher (CNA): VulnCheck · Vendor: nokogiri

Last updated 2026-09-01 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-25 16:17 UTCPublished CVE record published
2026-09-01 14:54 UTCUpdated Record last modified

nokogiri nokogiri UPGRADE

Affected: >= 1.5.1 and < 1.19.1

Fixed in: 1.19.1

Safe to downgrade to: a release before 1.5.1

1. Check installed version

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

2. UPGRADE to 1.19.1 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade nokogiri

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 1.5.1 (Debian / Ubuntu)

apt-cache madison nokogiri sudo apt install nokogiri=<VERSION_BEFORE_1.5.1> sudo apt-mark hold nokogiri

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

dnf --showduplicates list nokogiri sudo dnf downgrade nokogiri-<VERSION_BEFORE_1.5.1> sudo dnf versionlock add nokogiri

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-2026-79772?

nokogiri: upgrade to 1.19.1. Exact commands for each OS are on this page.

Is CVE-2026-79772 being exploited?

CVE-2026-79772 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-2026-79772 affect?

CVE-2026-79772 affects nokogiri. Severity is medium (CVSS 5.3). Nokogiri versions before 1.19.1 fail to check the return value from xmlC14NExecute in the canonicalize method, returning an empty string on failure instead of raising an exception. Attackers can exploit this to bypass signature validation i

How urgent is CVE-2026-79772?

Priority 30/100. Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-57235 HIGH 8.2 UPGRADE Nokogiri is an open source XML and HTML library for the Ruby programming language
CVE-2026-57236 HIGH 8.2 UPGRADE Nokogiri is an open source XML and HTML library for the Ruby programming language
CVE-2026-57434 HIGH 7.5 UPGRADE Nokogiri is an open source XML and HTML library for the Ruby programming language
CVE-2026-57435 HIGH 7.5 UPGRADE Nokogiri is an open source XML and HTML library for the Ruby programming language
CVE-2026-57436 MEDIUM 5.3 UPGRADE Nokogiri is an open source XML and HTML library for the Ruby programming language

References

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