CVE-2026-91859: MISP Access Log Entry Overwritten by Error Controller's Second beforeFilter Pass

Is it exploited?

Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of 29 Oct 2026. If CISA adds it, this page shows it as known exploited.

How likely is exploitation in the next 30 days?

0.5%

EPSS score, percentile 41 of all scored records. A probability estimated by FIRST, not a report of exploitation.

How severe?

5.3 Medium

CVSS v4.0 base score, given by the CNA

What should I do?

The fix introduces a per-instance boolean guard ($deferredWriterRegistered) in the AccessLog model so that logRequest() returns early on the second beforeFilter pass … Full textSolution from the CVE record.

CISA has set no required action, because the vulnerability is not in KEV.

Advisories and patches (1)

Which versions are affected?

Affected

• before 2.5.46

Versions by product

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026; CVE List, as of 29 Oct 2026. About the data.

What to do

Solution (from the CVE record)

The fix introduces a per-instance boolean guard ($deferredWriterRegistered) in the AccessLog model so that logRequest() returns early on the second beforeFilter pass, preventing the error controller from overwriting the original request's log entry. Additionally, a $this->create() call is added before $this->save() in saveOnShutdown() to ensure each save issues an INSERT rather than an UPDATE, providing defense-in-depth against accidental row mutation.

Advisories and patches

• Security patch (Patch)

This summary is based on the CVE record as of 29 Oct 2026. Check the vendor's advisory before you act: affected versions and fixes can change.

Affected products and versions

As listed in the CVE record.

Source: CVE List, as of 29 Oct 2026. About the data.

About this vulnerability

Affected versions of MISP can record incorrect access-log data for requests that terminate in an exception. Because CakeErrorController extends AppController, exception rendering runs the application startup path a second time. As a result, __accessMonitor() calls AccessLog::logRequest() twice for one HTTP request. The second deferred writer measures the error-controller execution instead of th…

Summary: CVE record, as of 29 Oct 2026.

• CISA has not added CVE-2026-91859 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
• The CVE record was published on 15 Sep 2026.
• The CVE record carries a CVSS v4.0 base score of 5.3 (Medium), given by its CNA.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.5% (percentile 41), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
• CISA's SSVC assessment in the CVE record: exploitation none, automatable no, technical impact partial.
• The credits in the CVE record name Anthropic (Claude) as finder.

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; CVE List, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026. About the data.

Description

MISP Access Log Entry Overwritten by Error Controller's Second beforeFilter Pass

Affected versions of MISP can record incorrect access-log data for requests that terminate in an exception. Because CakeErrorController extends AppController, exception rendering runs the application startup path a second time. As a result, __accessMonitor() calls AccessLog::logRequest() twice for one HTTP request. The second deferred writer measures the error-controller execution instead of the original request and can overwrite the row created by the first pass. The corrupted fields include request duration, SQL query count, memory usage, and potentially the recorded query log. The bug was masked because the same model instance retained the ID of the first saved row, causing the later save to issue an UPDATE rather than insert an obvious duplicate row. Version affected: ≤2.5.45

Source: CVE List, as of 29 Oct 2026. About the data.

Timeline