Is CVE-2026-100891 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-100891 being exploited in the wild.

How severe is CVE-2026-100891?

High severity, with a CVSS score of 7.3, published 28 September 2026.

Which products and versions are affected?

Trusted Domain Project OpenDMARC up to 1.4.2.

Is there a fix for CVE-2026-100891?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

How is CVE-2026-100891 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-100891?

Check whether you run Trusted Domain Project OpenDMARC at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-100891: Trusted Domain Project OpenDMARC encoding error in policy query

CVE-2026-100891 · Severity: high · CVSS 7.3 · Published 2026-09-28

OpenDMARC is a library used to validate DMARC email authentication policies. A vulnerability in the policy query function can be exploited remotely to cause an encoding error, potentially disrupting email authentication and validation. The vendor has not responded to disclosure attempts, leaving systems at risk.

Technologies: Trusted Domain Project OpenDMARC. Vendors: Trusted Domain Project.

Quick answers

Is CVE-2026-100891 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-100891 being exploited in the wild.
How severe is CVE-2026-100891?: High severity, with a CVSS score of 7.3, published 28 September 2026.
Which products and versions are affected?: Trusted Domain Project OpenDMARC up to 1.4.2.
Is there a fix for CVE-2026-100891?: No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-100891 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-100891?: Check whether you run Trusted Domain Project OpenDMARC at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The vulnerability exists in the opendmarc_policy_query_dmarc function within libopendmarc/opendmarc_policy.c, specifically in the Internationalized Domain Name Handler component. An encoding error in this function allows remote attackers to trigger the vulnerability without authentication or user interaction, potentially leading to policy validation bypass or service disruption. No vendor patch is available at this time.

Affected products

Trusted Domain Project OpenDMARC up to 1.4.2

Timeline

2026-09-28: disclosed
other: Vendor did not respond to early disclosure

References

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