Out-of-Bounds Read Vulnerability in OpenBSD's MPLS Functionality
CVE-2026-56099

6.9MEDIUM

Key Information:

Vendor

OpenBSD
Status
Src
Vendor
CVE Published:
18 June 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2026-56099?

An out-of-bounds read vulnerability exists in the mpls_do_error function within OpenBSD's network management system prior to commit 6a23123. This flaw allows remote attackers to exploit crafted MPLS frames containing 16 labels without the Bottom-of-Stack bit set. Successfully exploiting this issue may lead to potential disclosure of sensitive kernel stack memory, posing significant security risks.

Affected Version(s)

src 0

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2026-56099 - Proof of Concept

References

https://pop.argus-systems.ai/advisory/adv-040.html
technical-descriptionexploit
https://github.com/openbsd/src/commit/6a23123ec05f1eb29cf...
patch
https://www.vulncheck.com/advisories/openbsd-mpls-do-erro...
third-party-advisory

CVSS V4

Score:
6.9
Severity:
MEDIUM
Confidentiality:
Low
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

Argus Systems
.