CVE-2025-27219: In the CGI gem before 0.4.2 for Ruby, the CGI::Cookie.parse method in the CGI library contains a potential Den

This month

MEDIUM 5.8REMOTEUPGRADE

CVE-2025-27219 is a medium-severity flaw (CVSS 5.8) affecting cgi. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In the CGI gem before 0.4.2 for Ruby, the CGI::Cookie.parse method in the CGI library contains a potential Denial of Service (DoS) vulnerability. The method does not impose any limit on the length of the raw cookie value it processes. This oversight can lead to excessive resource consumption when parsing extremely large cookies.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.8 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.8% (top 42%)
CISA exploited list	No
Weakness	CWE-770
Published	2025-03-04
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: ruby-lang

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-03-04 00:15 UTCPublished CVE record published
2026-06-17 09:03 UTCUpdated Record last modified

ruby-lang cgi UPGRADE

Affected: < 0.3.5.1 · >= 0.4.0 and < 0.4.2 · 0.3.6

Fixed in: 0.3.5.1, 0.4.2

Safe to downgrade to: a release before 0.3.6

1. Check installed version

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

2. UPGRADE to 0.3.5.1 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade cgi

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 0.3.6 (Debian / Ubuntu)

apt-cache madison cgi sudo apt install cgi=<VERSION_BEFORE_0.3.6> sudo apt-mark hold cgi

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

dnf --showduplicates list cgi sudo dnf downgrade cgi-<VERSION_BEFORE_0.3.6> sudo dnf versionlock add cgi

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-2025-27219?

cgi: upgrade to 0.3.5.1, 0.4.2. Exact commands for each OS are on this page.

Is CVE-2025-27219 being exploited?

CVE-2025-27219 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-2025-27219 affect?

CVE-2025-27219 affects cgi. Severity is medium (CVSS 5.8). In the CGI gem before 0.4.2 for Ruby, the CGI::Cookie.parse method in the CGI library contains a potential Denial of Service (DoS) vulnerability. The method does not impose any limit on the length of the raw cookie value it processes. This

How urgent is CVE-2025-27219?

Priority 40/100. Remotely exploitable, no login, no user action

Software pages

Ruby vulnerabilities

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CVE-2025-27220 MEDIUM 4.0 UPGRADE In the CGI gem before 0.4.2 for Ruby, a Regular Expression Denial of Service (ReDoS) vulnerability exists in t

References

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