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No exploitation reportedFix available

CVE-2021-21317

No exploitation reported by the sources we read.

  • Published2021-02-16
  • Fixed in0.11.0
  • WeaknessCWE-1333 · CWE-400

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

uap-core in an open-source npm package which contains the core of BrowserScope's original user agent string parser. In uap-core before version 0.11.0, some regexes are vulnerable to regular expression denial of service (REDoS) due to overlapping capture groups. This allows remote attackers to overload a server by setting the User-Agent header in an HTTP(S) request to maliciously crafted long strings. This is fixed in version 0.11.0. Downstream packages such as uap-python, uap-ruby etc which depend upon uap-core follow different version schemes.

Timeline

dates in UTC
  1. 2021-02-1618:15CVE publishedNVD

Versions per branch

NVD · OSV
Uap-core project uap-core
BranchAffectedFixed in
0.11< 0.11.00.11.0

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • uap-coreUbuntu:26.10all versions · no fixed version listed
  • uap-coreUbuntu:26.04:LTSall versions · no fixed version listed
  • uap-coreUbuntu:25.10all versions · no fixed version listed
  • uap-coreUbuntu:24.04:LTSall versions · no fixed version listed
  • uap-coreUbuntu:22.04:LTSall versions · no fixed version listed
  • uap-coreUbuntu:20.04:LTSall versions · no fixed version listed

Full record on NVD

Fix

  1. Update Uap-core project uap-core to 0.11.0

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

  • CNACVSS 3.15.3known since 2026-10-23
  • NVDCVSS 3.15.3read 2026-10-23
  • NVDCVSS 2.05read 2026-10-23
  • CNAweakness (CWE)CWE-400known since 2026-10-23
  • NVDweakness (CWE)CWE-1333read 2026-10-23
  • FIRST EPSSEPSS score2.5 %2026-11-09
  • OSVaffected packages—
  • GitHub AdvisoriesadvisoryHIGH2021-02-01

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Published
2021-02-16
Last Modified
2026-06-17
NVD status
Modified
GitHub Advisory
GHSA-p4pj-mg4r-x6v4

Frequently asked questions

What is CVE-2021-21317?

uap-core in an open-source npm package which contains the core of BrowserScope's original user agent string parser. In uap-core before version 0.11.0, some regexes are vulnerable to regular expression denial of service (REDoS) due to overlapping capture groups. This allows remote attackers to overload a server by setting the User-Agent header in an HTTP(S) request to maliciously crafted long strings. This is fixed in version 0.11.0. Downstream packages such as uap-python, uap-ruby etc which depend upon uap-core follow different version schemes.

Is CVE-2021-21317 actively exploited?

Active exploitation of CVE-2021-21317 has not been confirmed. Its EPSS score was 2.5% on 2026-11-09, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-21317?

CVE-2021-21317 has a CVSS v3 base score of 5.3 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

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