Review reviewCritical

CVE-2026-39834

golang.org/x/crypto golang.org/x/crypto/ssh, crypto

When writing data larger than 4GB in a single Write call on an SSH channel, an integer overflow in the internal payload size calculation caused the write loop to spin indefinitely, sending empty packets without making progress. The size comparison now uses int64 to prevent truncation.

CVSS
9.1
EPSS
0.53%
41.6% percentile
CISA KEV
Not listed
Published
2026.05.22
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability0.53%
Technical severityCVSS 9.1

Vulnerability overview

When writing data larger than 4GB in a single Write call on an SSH channel, an integer overflow in the internal payload size calculation caused the write loop to spin indefinitely, sending empty packets without making progress. The size comparison now uses int64 to prevent truncation.

Affected product and versions

Product
golang.org/x/crypto golang.org/x/crypto/ssh, crypto
Affected versions
< 0.52.0
Fixed versions
0.52.0

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that golang.org/x/crypto golang.org/x/crypto/ssh, crypto and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
CWE
CWE-190