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CryptoApplication · Golang

CVE-2026-39834

CRITICAL · 9.1 CVSS v3.1 Published 2026-05-22
Fix available
A fix is available. Upgrade to 0.52.0 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

An integer overflow in SSH channel write operations occurs when writing data larger than 4GB in a single call. The internal payload size calculation uses a 32-bit integer that truncates the size, causing the write loop to spin indefinitely and send empty packets without making progress. The fix involves changing the size comparison to use int64.

MitigationUpgrade to the patched version where the size comparison uses int64 instead of a potentially truncated integer type to prevent the overflow condition.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
CryptoApplication
Affected:< 0.52.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check golang.org/x/crypto version in use
    Run 'go list -m golang.org/x/crypto' or inspect go.mod for 'golang.org/x/crypto' version directive
    Affected if Version is lower than v0.52.0 (e.g., v0.51.0, v0.50.0, etc.)
  2. Verify application uses crypto/ssh Channel Write
    Search codebase for calls to Channel.Write() method on ssh.Channel objects
    Affected if Code contains Channel.Write() or channel.Write() operations on ssh connections
  3. Identify potential large data writes
    Search for Write() calls that could pass buffers or data structures larger than 4GB in a single call, such as file transfers, streaming large files, or data serialization
    Affected if Application performs single Write() calls with data exceeding approximately 4.3GB (2^32 bytes)
  4. Check runtime behavior under large writes
    Monitor ssh channel write operations using application logs or network traffic analysis; look for stalled connections or excessive empty packets
    Affected if SSH connections hang or stall during large data transfers and network capture shows repeated empty packets without data progression

A system is affected if it uses golang.org/x/crypto version below 0.52.0 and performs single Write() calls larger than 4GB to an SSH channel, causing connection hangs and empty packet loops.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 0.52.0 or later
Fixed in 0.52.0
Interim mitigation

Upgrade to the patched version where the size comparison uses int64 instead of a potentially truncated integer type to prevent the overflow condition.

Recommended fix High confidence

0.52.0

  1. 1. Identify the golang.org/x/crypto package dependency in your go.mod file
  2. 2. Update the package to version 0.52.0 or later using 'go get golang.org/x/[email protected]' or 'go get golang.org/x/crypto@latest'
  3. 3. Verify the installed version is >= 0.52.0 by running 'go list -m golang.org/x/crypto'
  4. 4. Run 'go mod tidy' to clean up dependencies
  5. 5. Rebuild and test your application to ensure the upgrade functions correctly
Caveat Review the release notes between your current version and 0.52.0 for any potential breaking changes in the crypto package

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Crypto Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA3.0 h
16.0 hours of engineering $2,760
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,416.

Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-39834 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data