A flaw was found in crun. When crun is built with libkrun and a container is started rootful with passt networking (krun.use_passt), crun can… (CVE-2026-84042)
Affects crunSource GCVE Database
Not known to be exploited · CVSS 7.8 Medium.
Data as of 10/25/2026, 16:58:57 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 0% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 10 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wild: no evidence on record.
Not in CISA KEV and no source reports exploitation
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 2026-10-25.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
GitHubcontainers/crunpkg:github/containers/crunOther threats | Affected
| Fixed in– |
Ubuntu:20.04:LTScrunpkg:deb/ubuntu/crun?arch=source&distro=focalOther threats | Affected
| Fixed in– |
Ubuntu:22.04:LTScrunpkg:deb/ubuntu/crun?arch=source&distro=jammyOther threats | Affected
| Fixed in– |
Ubuntu:24.04:LTScrunpkg:deb/ubuntu/crun?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Ubuntu:26.10crunpkg:deb/ubuntu/crun?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu:26.04:LTScrunpkg:deb/ubuntu/crun?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
The recommended mitigation is to avoid running untrusted container images with crun built with libkrun and passt networking enabled (krun.use_passt) in rootful mode until a fixed version is released. Monitor vendor advisories for updates on patch availability.
Description
CVE-2026-84042 is a high-severity vulnerability in crun affecting versions 1.29 and later. When crun is built with libkrun and a container is started rootful with passt networking enabled (krun.use_passt), it allows execution of attacker-controlled payloads from the container image with host root privileges. This is a regression introduced in version 1.29 due to improper privilege management, resulting in privilege escalation to host root. Mitigation currently involves avoiding running untrusted container images with krun and passt networking until a fixed version is released.
Impact
The vulnerability allows an attacker to escalate privileges from a container to host root, potentially compromising the entire host system. This can lead to full control over the host by executing attacker-controlled payloads with root privileges. The CVSS score of 7.8 reflects high impact on confidentiality, integrity, and availability, though the attack vector is local with high attack complexity and requires low privileges but no user interaction.
Weaknesses
- CWE-269Improper Privilege Management (opens in a new tab)
Class weaknessLikelihood of exploit: MediumOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
References
- nvd.nist.gov/vuln/detail/CVE-2026-84042 (opens in a new tab)
- access.redhat.com/security/cve/CVE-2026-84042 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2531222 (opens in a new tab)
- github.com/containers/crun (opens in a new tab)
- github.com/containers/crun/ (opens in a new tab)
- ubuntu.com/security/CVE-2026-84042 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-84042 (opens in a new tab)