CVE-2026-59842Network attack vector

Server memory disclosure via short Curve25519 key

Published Jul 21, 2026 · Updated Jul 21, 2026

Out-of-bounds read in Red Hat libssh allows remote attackers to disclose server heap memory during GSSAPI key exchange. The ssh_server_gss_kex_process_init() function copies CURVE25519_PUBKEY_SIZE bytes from client_pubkey without first validating ssh_string_len(client_pubkey). Exploitation requires a libssh-based server with GSSAPI Curve25519 key exchange enabled; a short SSH_MSG_KEXGSS_INIT key exposes small amounts of adjacent heap memory.

CVSS severity3.7
Low
EPSS probability0.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in Red Hat libssh allows remote attackers to disclose server heap memory during GSSAPI key exchange. The ssh_server_gss_kex_process_init() function copies CURVE25519_PUBKEY_SIZE bytes from client_pubkey without first validating ssh_string_len(client_pubkey). Exploitation requires a libssh-based server with GSSAPI Curve25519 key exchange enabled; a short SSH_MSG_KEXGSS_INIT key exposes small amounts of adjacent heap memory.

The record

CVE
CVE-2026-59842
Published
Jul 21, 2026
Updated
Jul 21, 2026
Vendor
389 Directory Server
Product
Red Hat Enterprise Linux 10
Classifications
CWE-125, T1190
Attack vector
network
Privileges
unauthenticated

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 privilegesunauthenticated

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

5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
3.7Red Hat, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/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.

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

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-125Out-of-bounds Read
T1190Exploit Public-Facing Application

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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