Vulnerability · Published Jun 18, 2026 · Assigned by VulnCheck
CVE-2026-56099OpenBSD mpls_do_error Kernel Stack Memory Disclosure via MPLS Input
Medium 5.3
In plain English
A medium-severity out-of-bounds read in src from openbsd. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 43% of all known vulnerabilities).
Severity (CVSS 3.1)5.3Medium
Exploit odds (30 days)0.5%top 56.9% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
OpenBSD before commit 6a23123 (2026-06-18) contains an out-of-bounds read vulnerability in the mpls_do_error function within sys/netmpls/mpls_input.c that allows remote attackers to disclose kernel stack memory by sending crafted MPLS frames with 16 labels and no Bottom-of-Stack bit set.
Affected products (as reported)
Weakness: CWE-125 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
References
- https://pop.argus-systems.ai/advisory/adv-040.html technical-description, exploit
- https://github.com/openbsd/src/commit/6a23123ec05f1eb29cfcaae0f3a468b2e1983cfd patch
- https://www.vulncheck.com/advisories/openbsd-mpls-do-error-kernel-stack-memory-disclosure-via-mpls-input third-party-advisory
- http://www.openwall.com/lists/oss-security/2026/06/19/3
- http://seclists.org/fulldisclosure/2026/Jun/17