CVE-2026-59842: A flaw was found in libssh

Routine

LOW 3.7REMOTEWATCHLISTDOWNGRADEMITIGATEMITIGATE

CVE-2026-59842 is a low-severity flaw (CVSS 3.7) affecting libssh, hardened images, enterprise linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A flaw was found in libssh. During server-side GSSAPI key exchange, a client-supplied Curve25519 public key shorter than the expected length is copied without proper length validation, leading to an out-of-bounds heap read. This could allow a remote unauthenticated attacker to disclose small amounts of server memory.

Why this priority

Remotely exploitable, no login, no user action
On your watchlist

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

Risk facts

CVSS score	3.7 (Low)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 58%)
CISA exploited list	No
Weakness	CWE-125
Published	2026-07-21
Last modified	2026-09-22

Publisher (CNA): Red Hat, Inc. · Vendor: libssh · redhat

Last updated 2026-09-22 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-21 12:18 UTCPublished CVE record published
2026-09-22 19:47 UTCUpdated Record last modified

libssh libssh DOWNGRADE

Affected: 0.12.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 0.12.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 0.12.0 (Debian / Ubuntu)

apt-cache madison libssh sudo apt install libssh=<VERSION_BEFORE_0.12.0> sudo apt-mark hold libssh

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

dnf --showduplicates list libssh sudo dnf downgrade libssh-<VERSION_BEFORE_0.12.0> sudo dnf versionlock add libssh

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.

redhat hardened images MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy hardened-images || rpm -q hardened-images || hardened-images --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

redhat enterprise linux MITIGATE

Affected: 10.0 · 10.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 10.0

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.

redhat enterprise linux for els MITIGATE

Affected: 10.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 10.2

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.

redhat enterprise linux for eus MITIGATE

Affected: 10.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 10.2

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.

redhat enterprise linux for ibm z systems MITIGATE

Affected: 10.0 · 10.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 10.0

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-2026-59842?

libssh: downgrade or apply the listed mitigation; hardened images: mitigate or apply the listed mitigation; enterprise linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-59842 being exploited?

CVE-2026-59842 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-2026-59842 affect?

CVE-2026-59842 affects libssh, hardened images, enterprise linux. Severity is low (CVSS 3.7). A flaw was found in libssh. During server-side GSSAPI key exchange, a client-supplied Curve25519 public key shorter than the expected length is copied without proper length validation, leading to an out-of-bounds heap read. This could allow

How urgent is CVE-2026-59842?

Priority 33/100. Remotely exploitable, no login, no user action; On your watchlist

Related CVEs

CVE-2026-59849 LOW 3.1 UPGRADE MITIGATE A flaw was found in libssh
CVE-2026-15370 MEDIUM 6.7 UPGRADE MITIGATE A flaw was found in libssh
CVE-2026-59847 MEDIUM 5.9 UPGRADE MITIGATE A flaw was found in libssh
CVE-2026-59850 MEDIUM 4.3 MITIGATE MITIGATE A flaw was found in libssh
CVE-2026-59848 MEDIUM 5.3 MITIGATE MITIGATE A flaw was found in libssh

References

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