CVE-2026-56854Network attack vector

Authentication bypass via skipped source-address validation

Published Aug 28, 2026 · Updated Aug 28, 2026

Incorrect authorization in golang.org/x/crypto/ssh before 0.55.0 allows remote attackers to bypass source-address access controls. In connection.serverAuthenticate, permissions from four non-public-key callbacks bypass validation against the client's remote address. Exploitation requires a server to return a source-address restriction from an affected callback, after which an out-of-range client obtains the SSH access otherwise granted by that callback.

CVSS severity7.5
High
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect authorization in golang.org/x/crypto/ssh before 0.55.0 allows remote attackers to bypass source-address access controls. In connection.serverAuthenticate, permissions from four non-public-key callbacks bypass validation against the client's remote address. Exploitation requires a server to return a source-address restriction from an affected callback, after which an out-of-range client obtains the SSH access otherwise granted by that callback.

The record

CVE
CVE-2026-56854
Published
Aug 28, 2026
Updated
Aug 28, 2026
Vendor
golang.org/x/crypto
Product
golang.org/x/crypto/ssh
Classifications
CWE-346, CWE-863, T1021.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 28, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 28, 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 <0.55.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

golang.org/x/crypto · golang.org/x/crypto/sshversion=0 <0.55.0

Published CVSS scores

9.1Red HatCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
8.1Amazon LinuxCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
7.5CISA ADP VulnrichmentCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

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-346Origin Validation Error
CWE-863Incorrect Authorization
T1021.004Remote Services: SSH

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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