CVE-2026-100888 Trusted Domain Project CVE debrief

Who should care

Defenders responsible for OpenDKIM installations, especially those exposed to untrusted input, should assess their configurations and monitor for potential exploitation attempts. OpenDKIM installations, especially those exposed to untrusted input, should be assessed for potential exploitation attempts. The vulnerability affects OpenDKIM up to version 2.11.0, and the attack can be executed remotely.

Why it matters

A weakness in OpenDKIM's DKIM signature header selection can lead to an out-of-bounds write, allowing remote attackers to manipulate the argument 'h'. Defenders should prioritize verifying OpenDKIM installations and monitoring for potential exploitation attempts.

• Remote attackers may manipulate DKIM signature headers
• Potential for data tampering or authentication bypass
• Verification of OpenDKIM installations and configurations is required
• Remediation details are currently limited

Technical summary

The OpenDKIM library is vulnerable to an out-of-bounds write in the dkim_canon_selecthdrs function. This can be exploited remotely by manipulating the 'h' argument. The vulnerability affects OpenDKIM up to version 2.11.0, and the attack can be executed remotely. The CVE record and NVD entry provide limited information on affected versions and remediation. Defenders should prioritize verifying OpenDKIM installations, especially those exposed to untrusted input, and monitor for potential exploitation attempts. The exploit has been made public.

Defensive priority

Defenders should prioritize verifying OpenDKIM installations, especially those exposed to untrusted input, and monitor for potential exploitation attempts.

Recommended defensive actions

• Verify OpenDKIM installations and configurations
• Monitor for potential exploitation attempts
• Review and update DKIM signature header selection processes
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and NVD entry provide limited information on affected versions and remediation. Further verification is required to determine the scope of the vulnerability. OpenDKIM installations, especially those exposed to untrusted input, should be assessed for potential exploitation attempts. The exploit has been made public, and defenders should prioritize verifying OpenDKIM installations and monitoring for potential exploitation attempts.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.