Site administrators are facing two severe security vulnerabilities that security experts say could enable large-scale attacks and demand extensive cleanup work. The issues, detailed in security releases seen by Ars Technica, involve weak encryption in TLS certificates and a critical flaw in the PHP programming language used by content management systems such as WordPress and Drupal.
The PHP Foundation announced on X that it is releasing patches for two critical vulnerabilities rated 9.2 out of 10 on the severity scale. Before the release scheduled for 14:00 UTC, the group encouraged PHP users to be ready to update and said it would issue an earlier release if details became public or evidence of active exploitation emerged. The advisory followed a report showing video of a tool called PHP2Shell executing code on web servers running the latest versions of WordPress, MediaWiki, Symphony, Drupal and other PHP-based sites.
The security firm watchTowr said it has confirmed the vulnerability and that it affects every version from PHP 5 onward. According to watchTowr's FAQ on the exploit, an unverified report indicates the flaw would allow an attacker to run their own code on a server running PHP, potentially taking control of it. Another company, Sansec, said it expects mass attacks to begin within 15 minutes of the release, and some PHP-based websites could go down briefly as administrators rush to patch.
The TLS problem centers on eMudhra, an India-based firm that said eight of its intermediate CA certificates have been compromised. Those certificates chain to roots trusted by Mozilla, Microsoft, Apple and Chrome root programs and by many downstream trust stores, and the weakness lies in private keys that could let attackers forge credentials for a range of websites and apps. The key sizes were 4, 56, 66, 115, 155, 156, 230 and 237 bits rather than the usual 384, according to Hacker News and other reports, meaning anyone could recover them by testing just 256 possible numbers.
The eMudhra certificates were widely trusted by hosts including Cloudflare, as well as browsers, operating systems, IoT devices and other internet-connected hardware. With forged domain certificates, attackers could impersonate servers and intercept traffic. Mozilla, Google and Apple have blocked the compromised certificates in their browsers, but Mozilla security expert Dennis Jackson warned that a macOS utility may continue trusting them because it does not check revocation information, a trait that applies to many other clients as well. eMudhra has revoked the eight certificates and blamed a script used to generate them.
The biggest current risk is to VPNs, particularly where governments actively try to intercept traffic, though IoT devices, unmaintained servers and other parts of the net may also be affected. Cryptography engineer Filippo Valsorda told Ars that the cleanup will be massive and larger than Heartbleed, the TLS bug that caused mass attacks in 2014.
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