CVE-2026-48852Network attack vectorHinoki check available

Client crash via invalid elliptic-curve point addition

Published May 25, 2026 · Updated May 25, 2026

Reachable assertion in PuTTY 0.71 through 0.83 allows remote attackers to crash an SSH client during initial key exchange. The elliptic-curve addition code wrongly asserts when two Weierstrass-form points share a y-coordinate, which a crafted NIST ECDSA host key and signature can provoke. The trigger requires a malicious SSH server or a man-in-the-middle position; it terminates only the connecting process, without code execution.

CVSS severity3.7
Low
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Reachable assertion in PuTTY 0.71 through 0.83 allows remote attackers to crash an SSH client during initial key exchange. The elliptic-curve addition code wrongly asserts when two Weierstrass-form points share a y-coordinate, which a crafted NIST ECDSA host key and signature can provoke. The trigger requires a malicious SSH server or a man-in-the-middle position; it terminates only the connecting process, without code execution.

The record

CVE
CVE-2026-48852
Published
May 25, 2026
Updated
May 25, 2026
Vendor
PuTTY
Product
PuTTY
Classifications
CWE-617, T1499
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=0.71 <0.84

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

PuTTY · PuTTYversion=0.71 <0.84

Published CVSS scores

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.

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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-617Reachable Assertion
T1499Endpoint Denial of Service

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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