CVE-2026-54736 Phalcon: Non-constant-time HMAC verification in `Encryption\Crypt::decrypt` (timing side-channel)
Attackers can exploit a timing side-channel in Phalcon's decryption to forge valid HMAC tags, allowing tampered encrypted data to be accepted as authentic.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-54736?
CVE-2026-54736 is a high-severity vulnerability in cphalcon, published on 10 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Phalcon is a high-performance, full-stack PHP framework. Prior to 5.14.1, Phalcon\Encryption\Crypt::decrypt compares the attacker-supplied HMAC tag against the freshly computed HMAC using PHP/Zephir identity comparison, which lowers to a byte-wise comparison that returns early on the first differing byte. This observable timing discrepancy can allow an attacker to recover a valid tag byte-by-byte and attach it to a chosen IV and ciphertext so that decrypt() accepts tampered encrypted content as authentic. This issue is fixed in version 5.14.1.
Which versions are affected by CVE-2026-54736?
2 open source packages ship an affected version, including phalcon/cphalcon.
| Package | Affected | Fixed in |
|---|---|---|
phalcon/cphalcon Packagist | All versions | 5.14.1 |
phalcon/cphalcon Packagist | All versions | 5.14.1 |
How do I fix CVE-2026-54736?
Upgrade phalcon/cphalcon to 5.14.1 or later.
Is CVE-2026-54736 being exploited?
There is no known exploitation of CVE-2026-54736 in the wild and no public exploit code.
Sources
Also known as GHSA-8jqh-95g6-7jpj.