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🛡️ CVE-2026-39834 on Ubuntu — golang-go.crypto

⚪ Unknown ✅ No Known Exploit OSV
N/A
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

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.

Distribution advisory

This page covers CVE-2026-39834 as tracked by Ubuntu, for the package golang-go.crypto. The fix is available in version 1:0.47.0-1ubuntu0.1~esm1; earlier versions remain affected.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity high, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: None.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: High — total loss, or loss the attacker controls.

Weakness class

UBUNTU-CVE-2026-39834 is classified as CWE-190: Integer Overflow or Wraparound. Arithmetic produces a value too large for its type and wraps around, so a later size or bounds check passes when it should not.

Affected software

UBUNTU-CVE-2026-39834 is recorded against 4 packages.

  • golang-go.crypto (fixed in 1:0.47.0-1ubuntu0.1~esm1)
  • google-guest-agent (fixed in 20250506.01-0ubuntu2.1)
  • lxd (fixed in 3.0.3-0ubuntu1~18.04.2+esm3)
  • snapd

Timeline and source

Published on 22 May 2026 and last revised on 21 July 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

ubuntu.com (Report)
www.cve.org (Report)
go.dev (Report)
groups.google.com (Report)
go.dev (Report)
pkg.go.dev (Report)
github.com (Report)
ubuntu.com (Advisory)
ubuntu.com (Advisory)
ubuntu.com (Advisory)

Other advisories for this package

golang-go.crypto has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-190: Integer Overflow or Wraparound) in other software:

CVE-2026-39834 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity Unknown
CVSS Score N/A
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
CWE N/A
Public Exploit ✅ No
Source OSV
Published 2026-05-22
Updated 2026-08-20
Modified 2026-07-21
Fix URL N/A

Affected Packages

Software From version Fixed in
golang-go.crypto — 1:0.47.0-1ubuntu0.1~esm1
google-guest-agent — 20250506.01-0ubuntu2.1
lxd — 3.0.3-0ubuntu1~18.04.2+esm3
snapd — —

Exploit Protection

Are you running golang-go.crypto?

UBUNTU-CVE-2026-39834 carries CVSS 9.5 Critical rating. BotEraser checks your installation against this and other known CVE records, and blocks IPs associated with exploit activity.

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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