Predictive Vulnerability Intelligence.

Product

  • Product
  • Pricing
  • Documentation

Company

  • About
  • Partnerships
  • Blog
  • Support

Legal

  • Terms
  • Privacy
  • Data Licensing

© 2026 FAUCET Technologies LLC. All rights reserved.

CVE-2021-31999

27
FAUCET Score

CVE-2021-31999 is a critical vulnerability in Rancher versions prior to 2.5.9 and 2.4.16, stemming from a reliance on untrusted inputs in security decisions. This allows authenticated users to impersonate other users or groups within the cluster by forging "Impersonate-User" or "Impersonate-Group" headers. With a CVSS score of 8.8 (High), it presents a significant risk due to its low attack complexity and potential for complete compromise of confidentiality, integrity, and availability. There is currently no evidence of active exploitation, public exploit code, or significant community discussion surrounding this vulnerability.

Impacted Technologies

VendorProductVersion(s)CPE
< 2.4.16CPE matchmatch criteria
cpe:2.3:a:rancher:rancher:*:*:*:*:*:*:*:*
>= 2.5.0, < 2.5.9CPE matchmatch criteria
cpe:2.3:a:rancher:rancher:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

8.8HIGH

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
2.8
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.05%
Probability of exploitation in next 30 days
EPSS Percentile
60.8%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0105 is in the 57th percentile among its peer group of 17,844 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.3 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

gopatch availablevia ghsa
Product: github.com/rancher/rancherFixed in: 2.4.16
gopatch availablevia ghsa
Product: github.com/rancher/rancherFixed in: 2.5.9

Vendor Advisories (1)

goGHSA-pvxj-25m6-7vqrhigh

Rancher Privilege escalation vulnerability via malicious "Connection" header

Apr 24, 2024

References

bugzilla.suse.com / show_bug.cgi
Issue TrackingRelease NotesThird Party Advisory