CVE-2025-26465

Summary

A vulnerability was found in OpenSSH when the VerifyHostKeyDNS option is enabled. A machine-in-the-middle attack can be performed by a malicious machine impersonating a legit server. This issue occurs due to how OpenSSH mishandles error codes in specific conditions when verifying the host key. For an attack to be considered successful, the attacker needs to manage to exhaust the client's memory resource first, turning the attack complexity high.

Affected Software

VendorProductVersion RangeStatus
6.8p1 <= 9.9p1affected
Red HatRed Hat Enterprise Linux 80:8.0p1-26.el8_10 < *unaffected
Red HatRed Hat Enterprise Linux 80:8.0p1-26.el8_10 < *unaffected
Red HatRed Hat Enterprise Linux 90:8.7p1-45.el9 < *unaffected
Red HatRed Hat Enterprise Linux 90:8.7p1-45.el9 < *unaffected
Red HatRed Hat Enterprise Linux 9.4 Extended Update Support0:8.7p1-38.el9_4.5 < *unaffected
Red HatRed Hat Discovery 1.141.14.3-1748529279 < *unaffected

Weaknesses

  • CWE-390: Detection of Error Condition Without Action

Workarounds

This issue can be mitigated by disabling VerifyHostKeyDNS by setting that option to 'no' in an SSH client configuration file (such as /etc/ssh/ssh_config, ~/.ssh/config, or one of the files in the /etc/ssh/ssh_config.d/ directory). This is the default configuration in Red Hat Enterprise Linux.

For configurations that require VerifyHostKeyDNS to be enabled (set to either 'yes' or 'ask'), mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

ADP Enrichment

CVE Program Container

Additional References

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: poc
    • Automatable: no
    • Technical Impact: total

Additional References

Additional References

References