CVE-2026-57842 The NetBSD Foundation CVE debrief

Who should care

NetBSD system administrators, security teams, and developers responsible for maintaining systems with untrusted local users should be aware of this vulnerability. They should assess exposure, prioritize remediation, and verify msg_iovlen values to prevent potential exploitation. Additionally, they should review the COMPAT_NETBSD32 compatibility layer and implement fixes or mitigations provided by The NetBSD Foundation.

Why it matters

This vulnerability allows local users to potentially escalate privileges, cause system instability, or trigger a kernel panic. NetBSD system administrators and security teams should assess exposure and prioritize remediation.

• Local privilege escalation potential
• Kernel panic or memory corruption
• System instability or crash potential
• Verification of msg_iovlen values required

Technical summary

The vulnerability exists in msg_recv_copyin() within the COMPAT_NETBSD32 compatibility layer. A local user can trigger a kernel panic or memory corruption by calling recvmsg() with msg_iovlen between 9 and IOV_MAX. The issue arises from a missing return statement before the cleanup label on the success path, leading to a use-after-free and double-free vulnerability. This allows local users to potentially escalate privileges or cause system instability. NetBSD system administrators and security teams should assess exposure and prioritize remediation.

Defensive priority

High-priority assessment and remediation recommended for NetBSD systems, especially those with untrusted local users.

Recommended defensive actions

• Assess exposure: Identify NetBSD systems with untrusted local users and verify msg_iovlen values.
• Verify msg_recv_copyin() implementation: Review the COMPAT_NETBSD32 compatibility layer for the missing return statement.
• Apply patches or workarounds: Implement fixes or mitigations provided by The NetBSD Foundation.
• Monitor system logs: Watch for kernel panics or memory corruption indicators.
• Perform vulnerability scanning: Identify potential exposure in the environment.
• Implement compensating controls: Consider additional security measures for systems with untrusted local users.
• technicalSummary

Evidence notes

The vulnerability is caused by a missing return statement before the cleanup label on the success path in msg_recv_copyin(). This results in a use-after-free and double-free vulnerability. Local users can trigger a kernel panic or memory corruption by calling recvmsg() with msg_iovlen between 9 and IOV_MAX. The COMPAT_NETBSD32 compatibility layer is affected, and defenders should verify msg_iovlen values and review the implementation of msg_recv_copyin().

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.