CVE-2026-56099
OpenBSD mpls_do_error Kernel Stack Memory Disclosure via MPLS Input
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.
INFO
Published Date :
June 18, 2026, 8:16 p.m.
Last Modified :
July 14, 2026, 10:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 4.0 | MEDIUM | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update OpenBSD to the latest version.
- Apply the security patch for netmpls.
- Review MPLS input processing.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-56099.
| URL | Resource |
|---|---|
| https://github.com/openbsd/src/commit/6a23123ec05f1eb29cfcaae0f3a468b2e1983cfd | Patch |
| https://pop.argus-systems.ai/advisory/adv-040.html | Exploit Patch Third Party Advisory |
| https://www.vulncheck.com/advisories/openbsd-mpls-do-error-kernel-stack-memory-disclosure-via-mpls-input | Third Party Advisory |
| http://seclists.org/fulldisclosure/2026/Jun/17 | Exploit Mailing List Patch Third Party Advisory |
| http://www.openwall.com/lists/oss-security/2026/06/19/3 | Exploit Mailing List Patch Third Party Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-56099 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-56099
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-56099 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-56099 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by [email protected]
Jul. 14, 2026
Action Type Old Value New Value Changed Affected [{'repo': 'https://github.com/openbsd/src', 'vendor': 'openbsd', 'product': 'src', 'versions': [{'status': 'affected', 'version': '0', 'lessThan': '6a23123ec05f1eb29cfcaae0f3a468b2e1983cfd', 'versionType': 'git'}], 'defaultStatus': 'affected'}] [{'repo': 'https://github.com/openbsd/src', 'vendor': 'openbsd', 'product': 'src', 'versions': [{'status': 'affected', 'version': '0', 'lessThan': '6a23123ec05f1eb29cfcaae0f3a468b2e1983cfd', 'versionType': 'git'}], 'packageURL': 'pkg:github/openbsd/src', 'defaultStatus': 'affected'}] -
Initial Analysis by [email protected]
Jun. 27, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N Added CPE Configuration OR *cpe:2.3:o:openbsd:openbsd:*:*:*:*:*:*:*:* versions up to (excluding) 2026-06-18 Added Reference Type VulnCheck: https://github.com/openbsd/src/commit/6a23123ec05f1eb29cfcaae0f3a468b2e1983cfd Types: Patch Added Reference Type VulnCheck: https://pop.argus-systems.ai/advisory/adv-040.html Types: Exploit, Patch, Third Party Advisory Added Reference Type VulnCheck: https://www.vulncheck.com/advisories/openbsd-mpls-do-error-kernel-stack-memory-disclosure-via-mpls-input Types: Third Party Advisory Added Reference Type CVE: http://seclists.org/fulldisclosure/2026/Jun/17 Types: Exploit, Mailing List, Patch, Third Party Advisory Added Reference Type CVE: http://www.openwall.com/lists/oss-security/2026/06/19/3 Types: Exploit, Mailing List, Patch, Third Party Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 23, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-56099', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-06-23T20:44:12.654787Z'} -
CVE Modified by af854a3a-2127-422b-91ae-364da2661108
Jun. 21, 2026
Action Type Old Value New Value Added Reference http://seclists.org/fulldisclosure/2026/Jun/17 -
CVE Modified by af854a3a-2127-422b-91ae-364da2661108
Jun. 19, 2026
Action Type Old Value New Value Added Reference http://www.openwall.com/lists/oss-security/2026/06/19/3 -
New CVE Received by [email protected]
Jun. 18, 2026
Action Type Old Value New Value Added Affected [{'repo': 'https://github.com/openbsd/src', 'vendor': 'openbsd', 'product': 'src', 'versions': [{'status': 'affected', 'version': '0', 'lessThan': '6a23123ec05f1eb29cfcaae0f3a468b2e1983cfd', 'versionType': 'git'}], 'defaultStatus': 'affected'}] Added 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. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N Added CWE CWE-125 Added Reference https://github.com/openbsd/src/commit/6a23123ec05f1eb29cfcaae0f3a468b2e1983cfd Added Reference https://pop.argus-systems.ai/advisory/adv-040.html Added Reference https://www.vulncheck.com/advisories/openbsd-mpls-do-error-kernel-stack-memory-disclosure-via-mpls-input