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CVE-2026-17544: Php Out of Bounds Write (CVSS 8.1)

CVE-2026-17544 is a high severity out of bounds write in Php with a CVSS score of 8.1. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

Last updated: Aug 5, 2026

Quick answer

Direct answer

CVE-2026-17544 is a high severity out of bounds write in Php with a CVSS score of 8.1. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

Risk scores

CVSS base score
8.1HIGH
EPSS probability
0.43%
Higher than 35 percent of all CVEs
CISA KEV
Not listed
CVSS metricWhat it means
Attack vector (AV:N)Network: reachable remotely
Attack complexity (AC:L)Low complexity
Attack requirements (AT:N)No attack requirements
Privileges required (PR:N)No privileges required
User interaction (UI:N)No user interaction
Confidentiality (VC:H)High confidentiality impact
Integrity (VI:H)High integrity impact
Availability (VA:H)High availability impact

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:N/R:X/V:X/RE:X/U:X

About Php

CVE-2026-17544 affects Php, a product from Php. Before acting, confirm where Php runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.

What the flaw is

In plain terms: Attacker-provided inputs to bccomp() could lead to an out-of-bounds write with stack and heap corruption in PHP versions from 8.4.* before 8.4.24 and from 8.5.* before 8.5.9.

The weakness class is Out of Bounds Write. The program writes past the end of a buffer, a common path to code execution.

Based on its CVSS vector, the flaw can be reached over the network, needs no login, and needs no user interaction. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

Affected versions and timeline

FieldDetail
ProductPhp
Affected versionsPhp from 8.4.0 before 8.4.24; Php from 8.5.0 before 8.5.9
PublishedJul 30, 2026
Last modifiedAug 5, 2026
Added to CISA KEVNot listed
Assigning CNAsecurity@php.net

How to detect it

  • Inventory every instance of Php and record the running version against the affected range above.
  • Check external attack surface scans for internet facing instances of the component.
  • Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
  • Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.

How to fix it

  • Apply the fixed version of Php named in the vendor advisory.
  • If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
  • Rescan after the change to prove the exposure is gone, then close the ticket.

CTEM action plan

CTEM stageWhat to do for this CVE
ScopeAdd every business service that depends on Php to the current CTEM cycle.
DiscoverFind all instances, including shadow and cloud deployments, and record versions and exposure.
PrioritizeRank using EPSS and CVSS together with asset exposure and business impact.
ValidateConfirm the flaw is reachable and exploitable in your environment and that compensating controls work.
MobilizeAssign the fix to the asset owner with a due date matched to the priority, then verify closure.

CWE References

Technical References

Frequently asked questions

CVE-2026-17544 is a high severity out of bounds write in Php with a CVSS score of 8.1. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

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