HashiCorp Nomad CVE-2026-6959

Exploitation requires local access to the Nomad client host with high privileges (PR:H per CVSS), specifically the ability to create or influence symbolic links in filesystem paths that the Nomad process accesses during task execution or file handling. The attack is limited to the Nomad client role - Nomad server nodes are not explicitly indicated as affected. The attack vector is strictly local (AV:L); remote unauthenticated exploitation is not possible. The Nomad process user's filesystem permissions bound the impact - if Nomad runs as a restricted service account, the attacker can only access files readable or writable by that account. Non-default or non-high-privilege operator access modes would not satisfy the PR:H requirement. SSVC automatable status is 'no,' confirming this cannot be scaled or weaponized at mass.

The CVSS base score of 6.0 is driven primarily by the S:C (scope change) metric: the attack escapes the Nomad process boundary to affect host-level files. However, multiple converging signals indicate limited real-world urgency. AV:L requires local host access; PR:H requires high privileges on the Nomad client - both significantly constrain the attacker pool. EPSS at 0.01% (1st percentile) reflects near-zero observed exploitation probability. SSVC signals reinforce this: Exploitation: none, Automatable: no, Technical Impact: partial. The vulnerability is not in CISA KEV and no public exploit code has been identified. One notable tension exists: the CVE description explicitly describes 'arbitrary file read AND write,' yet the official vendor-provided CVSS vector assigns C:N (no confidentiality impact) despite file read capability implying some confidentiality exposure. This discrepancy should be verified with HashiCorp's advisory (HCSEC-2026-14). Overall, this is a real but low-urgency issue: organizations with strict least-privilege enforcement on Nomad operators are not at meaningful risk; those allowing broad local access to Nomad clients should prioritize patching.

A malicious Nomad operator with local shell access to a Nomad client node creates a symbolic link in a directory path that the Nomad process is expected to read from or write to during normal operations (such as artifact staging or log directories). When Nomad follows the symlink without validation, the operator achieves read or write of arbitrary files - for example, overwriting /etc/cron.d/ entries or reading /etc/shadow - as the Nomad process user, extending impact beyond the intended Nomad scope to the host OS. No public proof-of-concept is identified, but the technique is well-understood and straightforward for an actor with the required local privileges.