CVE-2025-70034: An issue pertaining to CWE-1333: Inefficient Regular Expression Complexity (4.19) was discovered in mscdex ssh

Routine

HIGH 7.5REMOTEDOWNGRADE

CVE-2025-70034 is a high-severity flaw (CVSS 7.5) affecting ssh2. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue pertaining to CWE-1333: Inefficient Regular Expression Complexity (4.19) was discovered in mscdex ssh2 v1.17.0.

Why this priority

High severity
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 70%)
CISA exploited list	No
Weakness	CWE-1333
Published	2026-03-09
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: mscdex

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-09 18:16 UTCPublished CVE record published
2026-06-17 10:03 UTCUpdated Record last modified

mscdex ssh2 DOWNGRADE

Affected: 1.17.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.17.0

1. Check installed version

apt-cache policy ssh2 || rpm -q ssh2 || ssh2 --version

2. No fixed release: DOWNGRADE to a release before 1.17.0 (Debian / Ubuntu)

apt-cache madison ssh2 sudo apt install ssh2=<VERSION_BEFORE_1.17.0> sudo apt-mark hold ssh2

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list ssh2 sudo dnf downgrade ssh2-<VERSION_BEFORE_1.17.0> sudo dnf versionlock add ssh2

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

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-2025-70034?

ssh2: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2025-70034 being exploited?

CVE-2025-70034 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-2025-70034 affect?

CVE-2025-70034 affects ssh2. Severity is high (CVSS 7.5). An issue pertaining to CWE-1333: Inefficient Regular Expression Complexity (4.19) was discovered in mscdex ssh2 v1.17.0.

How urgent is CVE-2025-70034?

Priority 39/100. High severity; Remotely exploitable, no login, no user action

References

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