CVE-2025-61770: Rack is a modular Ruby web server interface

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HIGH 7.5REMOTEUPGRADE

CVE-2025-61770 is a high-severity flaw (CVSS 7.5) affecting rack. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Rack is a modular Ruby web server interface. In versions prior to 2.2.19, 3.1.17, and 3.2.2, `Rack::Multipart::Parser` buffers the entire multipart preamble (bytes before the first boundary) in memory without any size limit. A client can send a large preamble followed by a valid boundary, causing significant memory use and potential process termination due to out-of-memory (OOM) conditions. Remote attackers can trigger large transient memory spik

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.9% (top 40%)
CISA exploited list	No
Weakness	CWE-400
Published	2025-10-07
Last modified	2026-10-19

Publisher (CNA): GitHub, Inc. · Vendor: rack

Last updated 2026-10-19 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-10-07 15:16 UTCPublished CVE record published
2026-10-19 16:10 UTCUpdated Record last modified

rack rack UPGRADE

Affected: < 2.2.19 · >= 3.1.0 and < 3.1.17 · >= 3.2.0 and < 3.2.2

Fixed in: 2.2.19, 3.1.17, 3.2.2

Safe to downgrade to: a release before 3.1.0

1. Check installed version

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

2. UPGRADE to 2.2.19 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade rack

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 3.1.0 (Debian / Ubuntu)

apt-cache madison rack sudo apt install rack=<VERSION_BEFORE_3.1.0> sudo apt-mark hold rack

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

dnf --showduplicates list rack sudo dnf downgrade rack-<VERSION_BEFORE_3.1.0> sudo dnf versionlock add rack

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-2025-61770?

rack: upgrade to 2.2.19, 3.1.17, 3.2.2. Exact commands for each OS are on this page.

Is CVE-2025-61770 being exploited?

CVE-2025-61770 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-2025-61770 affect?

CVE-2025-61770 affects rack. Severity is high (CVSS 7.5). Rack is a modular Ruby web server interface. In versions prior to 2.2.19, 3.1.17, and 3.2.2, `Rack::Multipart::Parser` buffers the entire multipart preamble (bytes before the first boundary) in memory without any size limit. A client can se

How urgent is CVE-2025-61770?

Priority 46/100. High severity; Remotely exploitable, no login, no user action

Software pages

Ruby vulnerabilities

Related CVEs

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References

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