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CVE-2026-56099

OpenBSD mpls_do_error Kernel Stack Memory Disclosure via MPLS Input

MEDIUM
5.3
CVSS Score
Published: June 18, 2026 at 07:29 PM UTC
Updated: October 26, 2026 at 11:10 AM UTC
1 product affected across 1 vendorOpenBSD

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Severity
MEDIUM5.3
Exploit prediction
EPSS 0.5%
SSVC
No known exploit

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

OpenBSD· Openbsd
95%
v < 2026-06-18
Affected range stops below 2026-6-18, so it looks safe — our inference, not a vendor statement

References (5)

Technical DescriptionExploitPatchThird Party Advisory
Source: cverecord
https://pop.argus-systems.ai/advisory/adv-040.html
Patch
Source: cverecord
https://github.com/openbsd/src/commit/6a23123ec05f1eb29cfcaae0f3a468b2e1983cfd
Third Party Advisory
Source: cverecord
https://www.vulncheck.com/advisories/openbsd-mpls-do-error-kernel-stack-memory-disclosure-via-mpls-input
ExploitMailing ListPatchThird Party Advisory
Source: af854a3a-2127-422b-91ae-364da2661108
http://www.openwall.com/lists/oss-security/2026/06/19/3
ExploitMailing ListPatchThird Party Advisory
Source: af854a3a-2127-422b-91ae-364da2661108
http://seclists.org/fulldisclosure/2026/Jun/17

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.3MEDIUMVulnCheck
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
LOW
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-125

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