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🛡️ CVE-2021-31999 — rancher

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-807 OSV
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Rancher Privilege escalation vulnerability via malicious "Connection" header

A vulnerability was discovered in Rancher 2.0.0 through the aforementioned patched versions, where a malicious Rancher user could craft an API request directed at the proxy for the Kubernetes API of a managed cluster to gain access to information they do not have access to. This is done by passing the "Impersonate-User" or "Impersonate-Group" header in the Connection header, which is then correctly removed by the proxy. At this point, instead of impersonating the user and their permissions, the request will act as if it was from the Rancher management server and incorrectly return the information. The vulnerability is limited to valid Rancher users with some level of permissions on the cluster. There is not a direct mitigation besides upgrading to the patched Rancher versions.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. Rated impact: confidentiality high, integrity high, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Attack requirements: None — no deployment-specific condition has to hold.
  • Privileges required: Low — an ordinary user account is enough.
  • User interaction: None — nobody has to be tricked into anything.
  • Confidentiality impact: High — total loss, or loss the attacker controls.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: High — total loss, or loss the attacker controls.

Weakness class

CVE-2021-31999 is classified as CWE-807: Reliance on Untrusted Inputs in a Security Decision. The product uses a protection mechanism that relies on the existence or values of an input, but the input can be modified by an untrusted actor in a way that bypasses the protection mechanism.

Affected software

CVE-2021-31999 is recorded against 1 package.

  • github.com/rancher/rancher

Timeline and source

Published on 10 June 2024 and last revised on 10 July 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

github.com (Advisory)
nvd.nist.gov (Advisory)
bugzilla.suse.com (Web)

Other advisories for this package

github.com/rancher/rancher has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-807: Reliance on Untrusted Inputs in a Security Decision) in other software:

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CWE CWE-807
Public Exploit ✅ No
Source OSV
Published 2024-06-10
Updated 2026-08-20
Modified 2026-07-10
Fix URL N/A

Affected Packages

Software From version Fixed in
github.com/rancher/rancher — —

Similar Threats

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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