CVE-2026-67278: MikroTik RouterOS accepts malformed RSA/PKCS#1 v1.5 signatures across RSA-based services, including TLS/X.509

Q: How do I fix CVE-2026-67278?

routeros: upgrade to 7.23.6, 7.24.3. Exact commands for each OS are on this page.

Q: Is CVE-2026-67278 being exploited?

CVE-2026-67278 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-67278 affect?

CVE-2026-67278 affects routeros. Severity is critical (CVSS 9.1). MikroTik RouterOS accepts malformed RSA/PKCS#1 v1.5 signatures across RSA-based services, including TLS/X.509 certificate validation and SSH host-key authentication. Because its trust store includes an e=3 root CA, an attacker controlling o

Q: How urgent is CVE-2026-67278?

Priority 46/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

CRITICAL 9.1REMOTEUPGRADE

CVE-2026-67278 is a critical-severity flaw (CVSS 9.1) affecting routeros. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

MikroTik RouterOS accepts malformed RSA/PKCS#1 v1.5 signatures across RSA-based services, including TLS/X.509 certificate validation and SSH host-key authentication. Because its trust store includes an e=3 root CA, an attacker controlling or redirecting an outbound RouterOS TLS connection can use the root’s public certificate - without its private key - to forge a trusted intermediate and issue certificates for arbitrary hostnames, enabling TLS s

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 82%)
CISA exploited list	No
Weakness	CWE-347
Published	2026-09-05
Last modified	2026-09-25

Publisher (CNA): CERT.PL · Vendor: mikrotik

Last updated 2026-09-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-05 20:17 UTCPublished CVE record published
2026-09-25 14:56 UTCUpdated Record last modified

mikrotik routeros UPGRADE

Affected: >= 7.0 and < 7.23.6 · >= 7.24 and < 7.24.3

Fixed in: 7.23.6, 7.24.3

Safe to downgrade to: a release before 7.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-67278?

routeros: upgrade to 7.23.6, 7.24.3. Exact commands for each OS are on this page.

Is CVE-2026-67278 being exploited?

CVE-2026-67278 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-67278 affect?

CVE-2026-67278 affects routeros. Severity is critical (CVSS 9.1). MikroTik RouterOS accepts malformed RSA/PKCS#1 v1.5 signatures across RSA-based services, including TLS/X.509 certificate validation and SSH host-key authentication. Because its trust store includes an e=3 root CA, an attacker controlling o

How urgent is CVE-2026-67278?

Priority 46/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

MikroTik vulnerabilities

Related CVEs

CVE-2026-67279 MEDIUM 6.5 EXPLOITED UPGRADE Mikrotik RouterOS Improper Enforcement of Behavioral Workflow Vulnerability
CVE-2026-67276 HIGH 8.1 UPGRADE RouterOS does not compare the complete RSA public key when matching an SSH authentication request to an author
CVE-2026-67281 HIGH 7.5 UPGRADE RouterOS WebFig contains an unauthenticated file-read vulnerability in the /jsproxy path where a newly allocat
CVE-2026-67277 HIGH 8.2 EXPLOITED UPGRADE MikroTik RouterOS Missing Authentication for Critical Function Vulnerability
CVE-2026-86060 CRITICAL 9.8 EXPLOITED UPGRADE MikroTik RouterOS Improper Neutralization of Argument Delimiters in a Command Vulnerability

References

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