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CVE-2026-121520VulnerabilityPublished

Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update

Affects Red HatSource GCVE Database

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Authoritative record:CVE-2026-121520· Medium 4.5

Not known to be exploited · CVSS 4.5 Medium : upgrade Red Hat BuildKit to 0.34.1 when convenient.

Data as of 6 Nov 2026, 11:23 UTC

CVSS 4.0 base score
4.5Medium
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (Docker)CVSS 4.04.5
EPSS
0.1% chance of exploitation in 30 days – higher than 3% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 0.34.1
CVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:N/SI:H/SA:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 3 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.

What to do

Upgrade BuildKit to 0.34.1.

Affected software

ProductAffectedFixed in
MobyBuildKitAffected
  • <0.34.1
Fixed in
  • 0.34.1
GitHubBuildKitpkg:github/BuildKitOther threatsAffected
  • <0.34.1
Fixed in
  • 0.34.1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Apply the official update to BuildKit v0.34.1 or the corresponding Red Hat builds (podman 6.1.4-1.3.hum1 and related packages) which restrict extended attribute modifications to the BuildKit state directory and prevent symlink traversal outside the build boundary. Until patched, restrict access to the BuildKit control API socket and network endpoints to trusted administrators using strict filesystem permissions and mutual TLS. In multi-tenant environments, isolate build execution within dedicated ephemeral virtual machines. Additional temporary mitigations include auditing setxattr syscalls, enforcing SELinux mandatory access controls, restricting filesystem sandboxing with Landlock LSM, running BuildKit in rootless mode, and dropping CAP_SYS_ADMIN and CAP_SETFCAP capabilities from the BuildKit daemon to limit potential exploitation.

Description

A vulnerability in BuildKit allows a client with access to the BuildKit control API to submit crafted build requests that set extended attributes on files outside the BuildKit state directory. This can lead to privilege escalation on the underlying system, especially in multi-tenant environments such as shared OpenShift build services. The issue primarily affects Linux build hosts and can be mitigated by restricting access to the BuildKit API and isolating build execution. An official update to BuildKit v0.34.1 or corresponding Red Hat builds addresses this flaw by confining extended attribute modifications to the BuildKit state directory and preventing symlink traversal outside the build boundary.

References

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