CVE-2026-73644: OpenDJ SASL PLAIN authzid bypassing the proxy ACI scope check

Should you act?

Critical, preconditions apply

Severe if exploited, but exploitation needs conditions that may not apply to you. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.4%, percentile 34: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 34% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Needs an account (low (any account)). Exposure depends on who can log in.
• Only applies if your dependency tree includes org.openidentityplatform.opendj:opendj-server-legacy (Maven) <= 5.1.1, fixed in 5.1.2. Check your lockfile, including transitive dependencies.

What it is

OpenDJ is an LDAPv3 compliant directory service. Prior to 5.1.2, the SASL PLAIN authorization identity path in opendj-server-legacy/src/main/java/org/opends/server/extensions/PlainSASLMechanismHandler.java checked the PROXIEDAUTH privilege but did not evaluate the mayProxy proxy ACI scope when an authzid resolved to a different user. Both dn: and u: or bare authzid forms could therefore let an authenticated account holding PROXIEDAUTH assume any resolvable non-root identity outside the identities permitted by its proxy ACI. The fix returns INVALIDCREDENTIALS (49) before password verification when the target authorization identity is not permitted. This issue is fixed in version 5.1.2.

From the GitHub advisory

Summary When a SASL PLAIN bind supplies an authorization identity (authzid) that resolves to a different user, PlainSASLMechanismHandler verified only the PROXIEDAUTH privilege and never evaluated the "proxy" access-control right (the mayProxy ACI scope check). As a result, any account holding the proxied-auth privilege could assume any resolvable non-root identity without being granted a proxy ACI for that target.

This diverges from every other proxy path in OpenDJ — the proxied-authorization controls (RFC 4370) and the DIGEST-MD5 / GSSAPI authzid handlers all require both the privilege and the mayProxy scope grant.

Impact Privilege escalation / authorization bypass: a holder of proxied-auth can act as arbitrary directory users beyond the scope intended by the deployment's proxy ACIs, defeating the ACI-based restriction on which identities may be impersonated. Root/Directory Manager is not assumable this way.

Fix Enforce the mayProxy scope check on the SASL PLAIN authzid path (both dn: and u:/bare forms), sharing one hasProxyAccess helper with the DIGEST-MD5/GSSAPI path. Denial returns INVALIDCREDENTIALS (49) before password verification — matching DIGEST-MD5/GSSAPI — so an unauthenticated client cannot distinguish a missing privilege from a missing ACI grant.

Workaround Restrict or revoke the proxied-auth privilege until upgraded.

Weakness type: CWE-285, CWE-639.

Product: org.openidentityplatform.opendj:opendj-server-legacy (Maven) · Assigned by: GitHub_M · Published: 2026-08-13

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: low (any account)
• User interaction: none
• Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.41% probability of exploitation activity in the next 30 days; percentile 34.

Timeline

• 2026-07-24 — GitHub-reviewed advisory GHSA-p279-2cqp-84jg published (critical)
• 2026-08-13 — CVE record published by GitHub_M
• 2026-08-18 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-p279-2cqp-84jg github.com
2. CVE.org record CVE-2026-73644 cve.org
3. NVD entry CVE-2026-73644 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com

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