high CVSS 7.5

CVE-2024-2757·PHP vulnerability

In PHP 8.3.* before 8.3.5, function mb_encode_mimeheader() runs endlessly for some inputs that contain long strings of non-space characters followed by a space. This could lead to a potential DoS attack if a hostile user sends data to an application that uses this function.

Severity
high
Software
PHP
Fixed in
8.3.5
Published
2024-04-29

Affected versions

From: 8.3.0

Until: 8.3.5

Fixed in: 8.3.5

How to fix this CVE

Upgrade PHP to version 8.3.5 or later to resolve a denial-of-service vulnerability in the mb_encode_mimeheader() function. This function could enter an infinite loop when processing specific malformed input patterns, allowing attackers to exhaust server resources. Immediate patching is recommended for production environments running PHP 8.3.0–8.3.4.

sudo dnf update php

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check your installed PHP version by running `php -v` and confirm if it falls within 8.3.0–8.3.4
  2. Step 2: Search your application codebase for calls to mb_encode_mimeheader() using `grep -r 'mb_encode_mimeheader' /var/www/`
  3. Step 3: Monitor system resource usage (CPU/memory) for unexpected spikes; check logs with `tail -f /var/log/syslog | grep -i 'php\|apache\|nginx'` for hangs or timeout errors
  4. Step 4: After patching, verify the new version with `php -v` and confirm it shows 8.3.5 or later, then restart PHP-FPM/Apache with `sudo systemctl restart php-fpm` or `sudo systemctl restart apache2`

FAQ

What is CVE-2024-2757?

CVE-2024-2757 is a denial-of-service vulnerability in PHP's mb_encode_mimeheader() function that causes infinite loops when processing certain input patterns containing long sequences of non-space characters followed by a space character.

Is CVE-2024-2757 being actively exploited?

No, CVE-2024-2757 is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog and no public exploits are currently available.

What versions of PHP are affected by CVE-2024-2757?

PHP versions 8.3.0 through 8.3.4 are affected; version 8.3.5 and later contain the fix.

How do I check if my server is vulnerable to CVE-2024-2757?

Run `php -v` to retrieve your installed version; if it returns 8.3.0–8.3.4 and your application uses mb_encode_mimeheader(), your system is vulnerable.

Does Defensia detect CVE-2024-2757?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If PHP is installed on a monitored server, CVE-2024-2757 will appear in your dashboard with remediation steps.

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References

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