Severity: High (CVSS 7.8)

Affected Systems: Linux Linux Kernel

Overview

rtmutex: Use waiter::task instead of current in remove_waiter()

A high vulnerability identified as CVE-2026-43499 has been disclosed.

In the Linux kernel, the following vulnerability has been resolved:

rtmutex: Use waiter::task instead of current in remove_waiter()

remove_waiter() is used by the slowlock paths, but it is also used for
proxy-lock rollback in rt_mutex_start_proxy_lock() when invoked from
futex_requeue().

In the latter case waiter::task is not current, but remove_waiter()
operates on current for the dequeue operation. That results in several
problems:

1) the rbtree dequeue happens without waiter::task::pi_lock being held

2) the waiter task's pi_blocked_on state is not cleared, which leaves a
dangling pointer primed for UAF around.

3) rt_mutex_adjust_prio_chain() operates on the wrong top priority waiter
task

Use waiter::task instead of current in all related operations in
remove_waiter() to cure those problems.

[ tglx: Fixup rt_mutex_adjust_prio_chain(), add a comment and amend the
changelog ]

Risk

CVSS and CISA data indicate the following:

  • Review the OpenCVE and vendor advisory for exploit conditions and impact

OpenCVE Analysis

CVSS v4.0 N/ACVSS v3.1 7.8 HighCVSS v3.0 N/ACVSS v2 N/AKEV noEPSS yesSSVC no

  • OpenCVE title: rtmutex: Use waiter::task instead of current in remove_waiter()
  • Severity score: High (CVSS 7.8)
  • EPSS score: 0.00125
  • Weaknesses: CWE-825
Attack VectorLocal
Attack ComplexityLow
Privileges RequiredLow
User InteractionNone
ScopeUnchanged
Confidentiality ImpactHigh
Integrity ImpactHigh
Availability ImpactHigh
Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Required Action

Review the OpenCVE detail page and linked vendor advisory, then apply the vendor-provided update or mitigation for the affected product.

Prioritize systems where the affected product is internet-facing, handles authentication, or runs with elevated privileges.

Verify Updates

Confirm whether your environment uses the affected product(s): Linux Linux Kernel.

After remediation, verify the installed version against the fixed or unaffected versions listed by the vendor.

Temporary Mitigation (if patch is not available)

Use the mitigation published by the vendor. If no vendor mitigation is available, reduce exposure to the affected product, restrict access to trusted users or networks, and increase monitoring until an update can be applied.

Recommendation

  • Use OpenCVE, vendor, and source references as the source of truth for affected versions and remediation
  • Patch or mitigate affected products after confirming exposure in your environment
  • Monitor affected systems for unusual activity until remediation is complete

Support

If you require assistance, please contact our support team.

Immediate action is strongly recommended to protect your infrastructure.

Source Details

Customer Responsibility and Backups

Before applying updates, mitigations, or configuration changes, customers should take and verify current backups or snapshots of affected systems.

Customers are responsible for managing their servers, validating their own backups, testing changes, and ensuring they can restore services if an update or mitigation causes an issue.



Thursday, July 9, 2026

« Back