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Fencer Vulns
medium 5.9

CVE-2022-21221 json

Directory Traversal

published 2022-03-17 4 y ago modified 2026-07-08 4 mo ago also GHSA-fx95-883v-4q4h , GO-2022-0355 , EUVD-2022-1419

cvss
5.9
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
2.5%
EPSS 2.5% chance of exploitation in 30 days, percentile 84%
public exploits
0
none known

Summary

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.

Patch / fix

  • go github.com/valyala/fasthttp 1.34.0
  • n/a github.com/valyala/fasthttp 1.34.0

Exploit prediction

2.50% chance of exploitation in the next 30 days, higher than 84% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • snyk.io https://snyk.io/vuln/SNYK-GOLANG-GITHUBCOMVALYALAFASTHTTP-2407866 referenced PoC, tagged "exploit" by a source, unverified
  • github.com https://github.com/valyala/fasthttp/issues/1226 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:P/I:N/A:N
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected packages

ecosystem package affected fixed in
go github.com/valyala/fasthttp
<1.34.0
1.34.0

Affected products

  • n/a github.com/valyala/fasthttp

Classification

Weakness
  • CWE-22 Improper Limitation of a Pathname to a Restricted Directory

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.