PatchTheCVECVE-2026-48850: PuTTY 0.72 before 0.84 has a double free in RSA KEX.
24
Routine
LOW 3.7REMOTEUPGRADE
CVE-2026-48850 is a low-severity flaw (CVSS 3.7) affecting putty. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
PuTTY 0.72 before 0.84 has a double free in RSA KEX.
Why this priority
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 3.7 (Low) |
| Attack vector | Network (remote) |
| Attack complexity | High |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.3% (top 75%) |
| CISA exploited list | No |
| Weakness | CWE-415 |
| Published | 2026-05-25 |
| Last modified | 2026-07-24 |
Last updated 2026-07-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
putty putty UPGRADE
Affected: >= 0.72 and < 0.84
Fixed in: 0.84
Safe to downgrade to: a release before 0.72
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 0.72 (Debian / Ubuntu)
apt-cache madison putty
sudo apt install putty=<VERSION_BEFORE_0.72>
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_0.72>
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.
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-2026-48850?
putty: upgrade to 0.84. Exact commands for each OS are on this page.
Is CVE-2026-48850 being exploited?
CVE-2026-48850 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-2026-48850 affect?
CVE-2026-48850 affects putty. Severity is low (CVSS 3.7). PuTTY 0.72 before 0.84 has a double free in RSA KEX.
How urgent is CVE-2026-48850?
Priority 24/100. Remotely exploitable, no login, no user action
Software pages
Related CVEs
- CVE-2026-48852 LOW 3.7 UPGRADE PuTTY 0.71 before 0.84 has an assertion failure in ECDSA signature verification.
- CVE-2026-48851 LOW 3.1 UPGRADE PuTTY 0.77 before 0.84 uses a copy of the PuTTY icon as a trust indication for TELNET data but the trust statu