CVE-2022-21221: The package github.com/valyala/fasthttp before 1.34.0 are vulnerable to Directory Traversal via the ServeFile

Q: How do I fix CVE-2022-21221?

fasthttp: upgrade to 1.34.0. Exact commands for each OS are on this page.

Q: Is CVE-2022-21221 being exploited?

CVE-2022-21221 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-2022-21221 affect?

CVE-2022-21221 affects fasthttp. Severity is medium (CVSS 5.9). The package github.com/valyala/fasthttp before 1.34.0 are vulnerable to Directory Traversal via the ServeFile function, due to improper sanitization. It is possible to be exploited by using a backslash %5c character in the path. **Note:** T

Q: How urgent is CVE-2022-21221?

Priority 52/100. Public exploit reference; Remotely exploitable, no login, no user action

This week

MEDIUM 5.9REMOTEUPGRADE

CVE-2022-21221 is a medium-severity flaw (CVSS 5.9) affecting fasthttp. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The package github.com/valyala/fasthttp before 1.34.0 are vulnerable to Directory Traversal via the ServeFile function, due to improper sanitization. It is possible to be exploited by using a backslash %5c character in the path. **Note:** This security issue impacts Windows users only.

Why this priority

Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.9 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	2.5% (top 15%)
CISA exploited list	No
Weakness	CWE-22
Published	2022-03-17
Last modified	2026-06-17

Publisher (CNA): Snyk · Vendor: fasthttp project

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

Am I affected?

Timeline

2022-03-17 12:15 UTCPublished CVE record published
2026-06-17 04:25 UTCUpdated Record last modified

fasthttp project fasthttp UPGRADE

Affected: < 1.34.0

Fixed in: 1.34.0

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 1.34.0 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade fasthttp

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-2022-21221?

fasthttp: upgrade to 1.34.0. Exact commands for each OS are on this page.

Is CVE-2022-21221 being exploited?

CVE-2022-21221 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-2022-21221 affect?

CVE-2022-21221 affects fasthttp. Severity is medium (CVSS 5.9). The package github.com/valyala/fasthttp before 1.34.0 are vulnerable to Directory Traversal via the ServeFile function, due to improper sanitization. It is possible to be exploited by using a backslash %5c character in the path. **Note:** T

How urgent is CVE-2022-21221?

Priority 52/100. Public exploit reference; Remotely exploitable, no login, no user action

Software pages

GitHub vulnerabilities · Windows vulnerabilities

References

← Back to latest CVEs