CVE-2026-48850Network attack vectorHinoki check available

Remote crash via RSA key double free

Published May 25, 2026 · Updated May 25, 2026

Double free in PuTTY 0.72 before 0.84 allows remote attackers to crash the SSH client during RSA key exchange. The RSA KEX error path calls ssh_rsakex_freekey on an unexpectedly short server key and then frees the already released outer structure again. A malicious server can force RSA KEX before host-key verification; the documented consequence is a client crash, with no controllable effect reported.

CVSS severity5.9
Medium
EPSS probability0.32%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Double free in PuTTY 0.72 before 0.84 allows remote attackers to crash the SSH client during RSA key exchange. The RSA KEX error path calls ssh_rsakex_freekey on an unexpectedly short server key and then frees the already released outer structure again. A malicious server can force RSA KEX before host-key verification; the documented consequence is a client crash, with no controllable effect reported.

The record

CVE
CVE-2026-48850
Published
May 25, 2026
Updated
May 25, 2026
Vendor
PuTTY
Product
PuTTY
Classifications
CWE-415, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 25, 2026CVE publishedPublication date reported by the CVE source.
  2. May 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0.72 <0.84

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

PuTTY · PuTTYversion=0.72 <0.84

Published CVSS scores

5.9NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
3.7MITRECVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-415Double Free
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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