CVE-2026-52906
HIGHIn the Linux kernel, the following vulnerability has been resolved: 9p: fix access mode flags being ORed instead of replaced Since commit 1f3e4142c0eb ("9p: convert to the new mount…
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Description
In the Linux kernel, the following vulnerability has been resolved:
9p: fix access mode flags being ORed instead of replaced
Since commit 1f3e4142c0eb ("9p: convert to the new mount API"), v9fs_apply_options() applies parsed mount flags with |= onto flags already set by v9fs_session_init(). For 9P2000.L, session_init sets V9FS_ACCESS_CLIENT as the default, so when the user mounts with "access=user", both bits end up set. Access mode checks compare against exact values, so having both bits set matches neither mode.
This causes v9fs_fid_lookup() to fall through to the default switch case, using INVALID_UID (nobody/65534) instead of current_fsuid() for all fid lookups. Root is then unable to chown or perform other privileged operations.
Fix by clearing the access mask before applying the user's choice.
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of the affected component has shipped for CVE-2026-52906 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-52906 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-52906. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-52906 in your dependencies?
O3 detects CVE-2026-52906 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.