CVE-2026-109618: PHP Memory Corruption Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 26 Oct 2026, 5 days after the CVE record was published.
- How likely is exploitation in the next 30 days?
- 100%
EPSS score, percentile 100 of all scored records
- How severe?
- 9.2 Critical
CVSS v4.0 base score, given by the CNA
- What should I do?
CISA deadline 29 Oct 2026. Apply mitigations in accordance with vendor instructions … Full text
- Which versions are affected?
Affected
- from 8.2.* to before 8.2.35
- from 8.3.* to before 8.3.36
- from 8.4.* to before 8.4.27
- from 8.5.* to before 8.5.12
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
What to do
Required action, set by CISA
Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
CISA due date for this action: 29 October 2026.
Workaround (from the CVE record)
Check the GitHub Security Advisory for mitigation strategies.
Advisories and patches
Linked from CISA's catalog entry
- https://www.php.net/
- https://www.cisa.gov/news-events/alerts/2026/10/21/critical-vulnerabilities-php-require-immediate-patching
- https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk
- https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk
- https://nvd.nist.gov/vuln/detail/CVE-2026-109618
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | from 8.2.* to before 8.2.35 |
| Affected | from 8.3.* to before 8.3.36 |
| Affected | from 8.4.* to before 8.4.27 |
| Affected | from 8.5.* to before 8.5.12 |
Versions not listed are: unaffected.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
About this vulnerability
PHP contains an out-of-memory corruption vulnerability that allows for unauthenticated remote code execution.
Summary: CISA's KEV catalog, as of 28 Oct 2026.
- CISA added CVE-2026-109618 to its Known Exploited Vulnerabilities (KEV) catalog on 26 Oct 2026.
- CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
- The due date CISA sets for the required action is 29 Oct 2026.
- The CVE record was published on 21 Oct 2026, 5 days before it was added to KEV.
- The CVE record carries a CVSS v4.0 base score of 9.2 (Critical), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 100% (percentile 100), as of 28 Oct 2026.
- CISA's SSVC assessment in the CVE record: exploitation none, automatable no, technical impact total.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.
Description
RCE via OOM corruption
PHP uses longjmp() for out-of-memory (OOM) errors to exit the current context and abort handling of the request. Some contexts may not properly account for this scenario and leave request memory in an uninitialized state before performing an allocation. The subsequent request cleanup procedure may read or branch on this memory. Multiple OOM strategies can consistently trigger this condition and lead to remote code execution (RCE).
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
Weakness
- CWE-416: Use after free
- CWE-755: Improper Handling of Exceptional Conditions
- CWE-824: Access of uninitialized pointer
- CWE-1325: Improperly controlled sequential memory allocation
- CWE-1419: Incorrect Initialization of Resource
Attack patterns (CAPEC)
- CAPEC-234: Hijacking a privileged process
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.
Timeline
| Date | Event |
|---|---|
| 21 Oct 2026 | CVE record published |
| 23 Oct 2026 | CVE record last updated |
| 26 Oct 2026 | Added to CISA KEV |
| 29 Oct 2026 | CISA due date for the required action |
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