CVE-2026-100888 - Vulnerability Details

- Trusted Domain Project OpenDKIM DKIM Signature Header Selection dkim-canon.c dkim_canon_selecthdrs out-of-bounds write

Description

A weakness has been identified in Trusted Domain Project OpenDKIM up to 2.11.0. This affects the function dkim_canon_selecthdrs of the file libopendkim/dkim-canon.c of the component DKIM Signature Header Selection. Executing a manipulation of the argument h can lead to out-of-bounds write. The attack can be executed remotely. The exploit has been made available to the public and could be used for attacks. The vendor was contacted early about this disclosure but did not respond in any way.

Published: 2026-09-27

Score: 6.9 Medium

EPSS: < 1% Very Low

KEV: No

Impact:

Action:

Analysis

Impact

The vulnerability resides in the DKIM Signature Header Selection component of Trusted Domain Project OpenDKIM, specifically in the dkim_canon_selecthdrs function. The flaw allows an attacker to manipulate the ’h’ argument, resulting in an out‑of‑bounds write that can corrupt memory, potentially leading to arbitrary code execution or other severe consequences. The official description indicates that exploit code is publicly available, underscoring the seriousness of the risk.

Affected Systems

Trusted Domain Project OpenDKIM releases up to and including version 2.11.0 are affected. Systems running these versions or earlier are vulnerable; newer versions are not listed as impacted.

Risk and Exploitability

The CVSS score of 6.9 classifies this as a medium‑severity vulnerability, and the EPSS score is currently unavailable. As the exploit is available to the public and can be launched remotely, the likelihood of exploitation in the wild is non‑negligible. The vulnerability is not present in the CISA KEV catalog, but its remote nature warrants immediate attention.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

Trusted Domain Project

OpenDKIM

affected

Version	Status	Constraints
`2.0`	affected	—
`2.1`	affected	—
`2.2`	affected	—
`2.3`	affected	—
`2.4`	affected	—
`2.5`	affected	—
`2.6`	affected	—
`2.7`	affected	—
`2.8`	affected	—
`2.9`	affected	—
`2.10`	affected	—
`2.11.0`	affected	—

No data.

Vendor Product Confidence Versions

Trusted Domain Project

Opendkim

100%

Version	Status	Scheme	Platform
`2.0`	affected	generic	—
`2.1`	affected	generic	—
`2.2`	affected	generic	—
`2.3`	affected	generic	—
`2.4`	affected	generic	—
`2.5`	affected	generic	—
`2.6`	affected	generic	—
`2.7`	affected	generic	—
`2.8`	affected	generic	—
`2.9`	affected	generic	—
`2.10`	affected	generic	—
`2.11.0`	affected	semver	—

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Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

Upgrade Trusted Domain Project OpenDKIM to the latest released version that removes the out‑of‑bounds write flaw.
If an upgrade cannot be performed immediately, isolate the OpenDKIM service from the public internet and limit outbound SMTP traffic to only trusted hosts.
Implement monitoring of DKIM signing logs and system memory usage to detect potential exploitation attempts.

Generated by OpenCVE AI on September 28, 2026 at 01:24 UTC.

Tracking

Sign in to view the affected projects.

Advisories

No advisories yet.

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact Low

Vulnerable System Integrity Impact Low

Vulnerable System Availability Impact Low

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact Low

Integrity Impact Low

Availability Impact Low

User Interaction None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact Low

Integrity Impact Low

Availability Impact Low

User Interaction None

Access Vector Network

Access Complexity Low

Authentication None

Confidentiality Impact Partial

Integrity Impact Partial

Availability Impact Partial

This CVE is not in the KEV list.

The EPSS score is 0.00293.

Exploitation poc

Automatable yes

Technical Impact partial

References

Link	Providers
https://vuldb.com/cve/CVE-2026-100888
https://vuldb.com/submit/917015
https://vuldb.com/vuln/410837
https://vuldb.com/vuln/410837/cti
https://weitongli.com/share/opendkim-h-tag-oob-write.html

History

Wed, 30 Sep 2026 23:30:00 +0000

Type	Values Removed	Values Added
Metrics		ssvc `{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}`

Sun, 27 Sep 2026 23:45:00 +0000

Type	Values Removed	Values Added
Description		A weakness has been identified in Trusted Domain Project OpenDKIM up to 2.11.0. This affects the function dkim_canon_selecthdrs of the file libopendkim/dkim-canon.c of the component DKIM Signature Header Selection. Executing a manipulation of the argument h can lead to out-of-bounds write. The attack can be executed remotely. The exploit has been made available to the public and could be used for attacks. The vendor was contacted early about this disclosure but did not respond in any way.
Title		Trusted Domain Project OpenDKIM DKIM Signature Header Selection dkim-canon.c dkim_canon_selecthdrs out-of-bounds write
First Time appeared		Trusted Domain Project Trusted Domain Project opendkim
Weaknesses		CWE-119 CWE-787
CPEs		cpe:2.3:a:trusted_domain_project:opendkim::::::::
Vendors & Products		Trusted Domain Project Trusted Domain Project opendkim
References		https://vuldb.com/cve/CVE-2026-100888 https://vuldb.com/submit/917015 https://vuldb.com/vuln/410837 https://vuldb.com/vuln/410837/cti https://weitongli.com/share/opendkim-h-tag-oob-write.html
Metrics		cvssV2_0 `{'score': 7.5, 'vector': 'AV:N/AC:L/Au:N/C:P/I:P/A:P/E:POC/RL:ND/RC:C'}` cvssV3_0 `{'score': 7.3, 'vector': 'CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L/E:P/RL:X/RC:C'}` cvssV3_1 `{'score': 7.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L/E:P/RL:X/RC:C'}` cvssV4_0 `{'score': 6.9, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P'}`

Subscriptions

Trusted Domain Project Opendkim

MITRE

Status: PUBLISHED

Assigner: VulDB

Published: 2026-09-27T23:30:16.015Z

Updated: 2026-09-30T22:16:22.497Z

Reserved: 2026-09-27T07:35:52.389Z

Link: CVE-2026-100888

Vulnrichment

Updated: 2026-09-30T22:16:18.665Z

NVD

Status : Deferred

Published: 2026-09-28T00:16:32.473

Modified: 2026-09-30T23:16:57.013

Link: CVE-2026-100888

Redhat

No data.

OpenCVE Enrichment

Updated: 2026-09-28T16:23:42Z

Weaknesses

CWE-119
Improper Restriction of Operations within the Bounds of a Memory Buffer
CWE-787
Out-of-bounds Write

Impact

Affected Systems

Risk and Exploitability

Tracking

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact Low

Vulnerable System Integrity Impact Low

Vulnerable System Availability Impact Low

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact Low

Integrity Impact Low

Availability Impact Low

User Interaction None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact Low

Integrity Impact Low

Availability Impact Low

User Interaction None

Access Vector Network

Access Complexity Low

Authentication None

Confidentiality Impact Partial

Integrity Impact Partial

Availability Impact Partial

Exploitation poc

Automatable yes

Technical Impact partial

Subscriptions

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