CVE-2026-48851: PuTTY 0.77 before 0.84 uses a copy of the PuTTY icon as a trust indication for TELNET data but the trust statu

Routine

LOW 3.1UPGRADE

CVE-2026-48851 is a low-severity flaw (CVSS 3.1) affecting putty. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

PuTTY 0.77 before 0.84 uses a copy of the PuTTY icon as a trust indication for TELNET data but the trust status is not cleared between proxy authentication and the main session.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	3.1 (Low)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.2% (top 87%)
CISA exploited list	No
Weakness	CWE-451
Published	2026-05-25
Last modified	2026-07-24

Publisher (CNA): MITRE · Vendor: putty

Last updated 2026-07-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-25 21:16 UTCPublished CVE record published
2026-07-24 10:10 UTCUpdated Record last modified

putty putty UPGRADE

Affected: >= 0.77 and < 0.84

Fixed in: 0.84

Safe to downgrade to: a release before 0.77

1. Check installed version

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

2. UPGRADE to 0.84 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade putty

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade putty

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 0.77 (Debian / Ubuntu)

apt-cache madison putty sudo apt install putty=<VERSION_BEFORE_0.77> sudo apt-mark hold putty

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list putty sudo dnf downgrade putty-<VERSION_BEFORE_0.77> sudo dnf versionlock add putty

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-2026-48851?

putty: upgrade to 0.84. Exact commands for each OS are on this page.

Is CVE-2026-48851 being exploited?

CVE-2026-48851 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-2026-48851 affect?

CVE-2026-48851 affects putty. Severity is low (CVSS 3.1). PuTTY 0.77 before 0.84 uses a copy of the PuTTY icon as a trust indication for TELNET data but the trust status is not cleared between proxy authentication and the main session.

How urgent is CVE-2026-48851?

Priority 14/100. No elevated risk signals yet.

Software pages

PuTTY vulnerabilities

Related CVEs

CVE-2026-48850 LOW 3.7 UPGRADE PuTTY 0.72 before 0.84 has a double free in RSA KEX.
CVE-2026-48852 LOW 3.7 UPGRADE PuTTY 0.71 before 0.84 has an assertion failure in ECDSA signature verification.

References

← Back to latest CVEs