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PHPApplication

CVE-2026-7259

MEDIUM · 6.5 CVSS v3.1 Published 2026-05-10
Fix available
A fix is available. Upgrade to 8.2.31 / 8.3.31 or later.
See remediation →
72/100
Remediation priority · Elevated
Remotely reachable No privileges

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In PHP versions 8.2.* before 8.2.31, 8.3.* before 8.3.31, 8.4.* before 8.4.21, and 8.5.* before 8.5.6, a mismatch between encoding lists in Oniguruma and mbfl leads to  a NULL pointer dereference, resulting in a segmentation fault and denial of service. The vulnerability is exploitable when user-controlled input can influence the encoding passed to mb_regex_encoding().

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

In PHP versions 8.2.* before 8.2.31, 8.3.* before 8.3.31, 8.4.* before 8.4.21, and 8.5.* before 8.5.6, a mismatch between encoding lists in the Oniguruma regex library and mbfl (multibyte filter) leads to a NULL pointer dereference when user-controlled input is passed to mb_regex_encoding(). This causes a segmentation fault resulting in denial of service.

MitigationUpgrade PHP to version 8.2.31, 8.3.31, 8.4.21, or 8.5.6 or later. Additionally, validate and sanitize any user input before passing it to mb_regex_encoding() to prevent exploitation.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
PHPApplication
Affected:>= 8.2.0, < 8.2.31>= 8.3.0, < 8.3.31>= 8.4.0, < 8.4.21>= 8.5.0, < 8.5.6

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check installed PHP version
    Run `php -v` or view phpinfo() output to identify the exact PHP version
    Affected if Version is 8.2.0 through 8.2.30, 8.3.0 through 8.3.30, 8.4.0 through 8.4.20, or 8.5.0 through 8.5.5
  2. Verify mbstring extension is loaded
    Run `php -m` and look for mbstring, or check phpinfo() for the mbstring section
    Affected if The mbstring extension is enabled and the PHP version is in the affected range
  3. Identify mb_regex_encoding usage in code
    Search application source code for calls to mb_regex_encoding() function and examine whether any user-supplied input (from $_GET, $_POST, $_COOKIE, or similar sources) flows into the encoding parameter
    Affected if User-controlled input directly influences the encoding argument passed to mb_regex_encoding()
  4. Confirm Oniguruma regex library is in use
    Check phpinfo() for Oniguruma regex library support, or verify that the regex.encoding INI setting defaults to Oniguruma
    Affected if Oniguruma is the active regex library and the PHP version is vulnerable

Environment is affected if running a vulnerable PHP version (8.2.x before 8.2.31, 8.3.x before 8.3.31, 8.4.x before 8.4.21, or 8.5.x before 8.5.6) with mbstring enabled and user input flowing to mb_regex_encoding()

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 8.2.31 / 8.3.31 / 8.4.21 or later
Fixed in 8.2.318.3.318.4.21
Interim mitigation

Upgrade PHP to version 8.2.31, 8.3.31, 8.4.21, or 8.5.6 or later. Additionally, validate and sanitize any user input before passing it to mb_regex_encoding() to prevent exploitation.

Recommended fix High confidence

PHP 8.2.31 / 8.3.31 / 8.4.21 / 8.5.6 (minimum fixed version based on your current major line)

  1. 1. Identify the current PHP version using 'php -v' or 'phpinfo()'
  2. 2. Identify the package manager or installation method used (apt, yum, dnf, brew, source compile, etc.)
  3. 3. For package manager installations: update the package repository and upgrade PHP to the latest available version in your minor line
  4. 4. For apt-based systems (Debian/Ubuntu): run 'sudo apt update && sudo apt upgrade php' or add Ondrej Sury's PPA for newer PHP versions
  5. 5. For yum/dnf-based systems (RHEL/CentOS/Fedora): run 'sudo dnf update php*' or 'sudo yum update php*'
  6. 6. For brew (macOS): run 'brew update' and 'brew upgrade php'
  7. 7. After upgrade, verify the installed version with 'php -v' to confirm it meets the minimum fixed version (8.2.31, 8.3.31, 8.4.21, or 8.5.6)
  8. 8. Test critical application functionality to ensure the upgrade does not break existing features
Caveat Standard PHP minor version upgrades typically have backward compatibility, but test thoroughly as mbstring behavior changes may affect encoding-dependent code

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in PHP Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-7259 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data