CVE-2026-59849Network attack vector

Client hang via stalled certificate iterator

Published Jul 21, 2026 · Updated Jul 21, 2026

Infinite loop in libssh for affected Red Hat products allows remote authenticated users to hang clients during certificate authentication. The ssh_userauth_publickey_auto() routine in src/auth.c fails to advance its certificate-candidate iterator when a configured certificate is absent or rejected, so it restarts the same attempts indefinitely. Reachability requires a specific non-default certificate configuration and a connection to a server that repeatedly rejects the certificate; the resulting client-side loop consumes resources and prevents authentication from completing.

CVSS severity3.1
Low
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Infinite loop in libssh for affected Red Hat products allows remote authenticated users to hang clients during certificate authentication. The ssh_userauth_publickey_auto() routine in src/auth.c fails to advance its certificate-candidate iterator when a configured certificate is absent or rejected, so it restarts the same attempts indefinitely. Reachability requires a specific non-default certificate configuration and a connection to a server that repeatedly rejects the certificate; the resulting client-side loop consumes resources and prevents authentication from completing.

The record

CVE
CVE-2026-59849
Published
Jul 21, 2026
Updated
Jul 21, 2026
Vendor
389 Directory Server
Product
Red Hat Enterprise Linux 10
Classifications
CWE-835, T1499
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 21, 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?

Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

389 Directory Server · Red Hat Enterprise Linux 10Affected versions are unavailable in this record.
389 Directory Server · Red Hat Hardened ImagesAffected versions are unavailable in this record.

Published CVSS scores

3.1Red HatCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
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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