WordPressCMS
CVE-2011-4957
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 · uneditedThe make_clickable function in wp-includes/formatting.php in WordPress before 3.1.1 does not properly check URLs before passing them to the PCRE library, which allows remote attackers to cause a denial of service (crash) via a comment with a crafted URL that triggers many recursive calls.
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 confidenceThe make_clickable function in WordPress before 3.1.1 (wp-includes/formatting.php) does not properly validate URLs before passing them to the PCRE library. A remote attacker can embed a crafted URL in a comment that triggers excessive recursive calls, causing a denial of service via crash.
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
WordPressCMS
<= 3.1= 0.71= 1.0= 1.0.1= 1.0.2= 1.1.1= 1.2= 1.2.1= 1.2.2= 1.2.3= 1.2.4= 1.2.5CVSS 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
- Authentication
- None
- Confidentiality
- None
- Integrity
- None
- Availability
- Partial
AV:N/AC:L/Au:N/C:N/I:N/A:P
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 checksWork through these to decide whether this CVE applies to you.
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Determine installed WordPress versionCheck the version defined in wp-includes/version.php (look for $wp_version variable) or view the Dashboard > At a Glance pageAffected if Version is 3.1 or earlier, or matches one of the old affected versions (0.71, 1.0, 1.0.1, 1.0.2, 1.1.1, 1.2 through 1.2.5)
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Locate make_clickable functionExamine the file wp-includes/formatting.php and search for the function definition 'function make_clickable'Affected if The file exists and contains this function (pre-3.1.1 versions are vulnerable)
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Verify comments are enabledCheck WordPress settings under Settings > Discussion, or inspect the database table wp_options for option_name 'comment_registration' or 'default_comment_status'Affected if Comments or pingbacks are open on the site, as the attack vector is through crafted URLs in comments
You are affected if your WordPress version is 3.1 or earlier (including the listed old versions) and comments are enabled, allowing malicious URLs to trigger the recursive PCRE issue in make_clickable.
Generated from the published advisory. Verify against your own configuration.
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.
From vendor dataUpgrade WordPress to version 3.1.1 or later to obtain the patched make_clickable function with proper URL validation and recursion limits.
Fix this in WordPress
Scoped from the published advisory
- Consultation2.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,224.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2011-4957 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2011-4957 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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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.
- 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