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Zero Downtime · Monday · 53 min

PHP2Shell Zero-Days Hit, Certificate Authority’s Private Key Was Literally 4

PHP had the kind of week that makes system administrators look at a cornfield and reconsider their career choices. Two critical remote code execution vulnerabilities, emergency patches, and a race to exploit them. Meanwhile, a certificate authority trusted to help authenticate the internet managed to produce a private key with the numerical value of four. This week, John and Logan break down the PHP2Shell story and the eMudhra certificate authority incident where the cryptography was not defeated. Someone just counted. Stories in this episode: PHP2Shell: critical bugs, emergency patches, and the race to exploit PHP. CVE-2026-109618 and CVE-2026-109619 both carry a critical 9.2 CVSS v4 rating. The first involves running out of memory at a particularly bad moment during request initialization. The second is a use-after-free where internal state survives after the memory it refers to has been freed. Researchers demonstrated working remote code execution from both. Apache with mod_php behaves differently than PHP-FPM, and that affects the attack. Amazon says its MadPot honeypots recorded exploitation attempts four days before public disclosure. Sansec revised its initial assessment on October 22 to say mass exploitation appeared less likely than first expected because attacks needed specific knowledge and conditions on the target. Emergency fixed releases are 8.2.35, 8.3.36, 8.4.27, and 8.5.12. Restart the workers after updating. eMudhra: the certificate authority whose private key was literally 4. Eight compromised intermediate CA keys were small integers. Mozilla independently confirmed that all eight were below 256 and could be recovered almost instantly. Six were for TLS, two for code signing. These were elliptic curve keys using P-384, where the secret is supposed to be selected unpredictably from an enormous range. eMudhra says the affected intermediates were created during an April 30, 2025 key generation ceremony using FIPS 140-2 Level 3 certified hardware security modules, and a wrap-and-unwrap step produced a weak set of keys alongside the intended strong ones. The problem remained undetected for about 18 months through two independent audit cycles. eMudhra revoked all eight intermediates on October 18 and has now stated it is exiting the public TLS business. New episodes weekly. Follow Zero Downtime for cybersecurity, AI, privacy, and the tech stories that actually matter.

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PHP had the kind of week that makes system administrators look at a cornfield and reconsider their career choices. Two critical remote code execution vulnerabilities, emergency patches, and a race to exploit them. Meanwhile, a certificate authority trusted to help authenticate the internet managed to produce a private key with the numerical value of four. This week, John and Logan break down the PHP2Shell story and the eMudhra certificate authority incident where the cryptography was not defeated. Someone just counted.

Stories in this episode:

PHP2Shell: critical bugs, emergency patches, and the race to exploit PHP. CVE-2026-109618 and CVE-2026-109619 both carry a critical 9.2 CVSS v4 rating. The first involves running out of memory at a particularly bad moment during request initialization. The second is a use-after-free where internal state survives after the memory it refers to has been freed. Researchers demonstrated working remote code execution from both. Apache with mod_php behaves differently than PHP-FPM, and that affects the attack. Amazon says its MadPot honeypots recorded exploitation attempts four days before public disclosure. Sansec revised its initial assessment on October 22 to say mass exploitation appeared less likely than first expected because attacks needed specific knowledge and conditions on the target. Emergency fixed releases are 8.2.35, 8.3.36, 8.4.27, and 8.5.12. Restart the workers after updating.

eMudhra: the certificate authority whose private key was literally 4. Eight compromised intermediate CA keys were small integers. Mozilla independently confirmed that all eight were below 256 and could be recovered almost instantly. Six were for TLS, two for code signing. These were elliptic curve keys using P-384, where the secret is supposed to be selected unpredictably from an enormous range. eMudhra says the affected intermediates were created during an April 30, 2025 key generation ceremony using FIPS 140-2 Level 3 certified hardware security modules, and a wrap-and-unwrap step produced a weak set of keys alongside the intended strong ones. The problem remained undetected for about 18 months through two independent audit cycles. eMudhra revoked all eight intermediates on October 18 and has now stated it is exiting the public TLS business.

New episodes weekly. Follow Zero Downtime for cybersecurity, AI, privacy, and the tech stories that actually matter.

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