Phalcon: Non-constant-time HMAC verification in `Encryption\Crypt::decrypt` (timing side-channel)
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- High
- Attack requirements
- None
- Impact type
- Information disclosure, Security bypass
- Confidentiality · integrity · availability
- None · High · None
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub. Impact type from CWE-208 and CWE-347.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| phalcon | cphalcon | before 5.14.1 | 5.14.1 | Patch available | CNA |
| — | phalcon/cphalcon (Packagist) | before 5.14.1 | 5.14.1 | Patch available | GHSA-8jqh-95g6-7jpj |
- cphalcon Vendorphalcon Affected before 5.14.1 Fixed in 5.14.1 Patch available CNA
- phalcon/cphalcon (Packagist) Vendor— Affected before 5.14.1 Fixed in 5.14.1 Patch available GHSA-8jqh-95g6-7jpj
Remediation
- Fix · CNA cphalcon (phalcon) Fixed in 5.14.1
- Fix · GHSA-8jqh-95g6-7jpj phalcon/cphalcon (Packagist) Fixed in 5.14.1 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-54736
- 2026-10-03 Alias added: GHSA-8jqh-95g6-7jpj
References
Other 6
- https://github.com/phalcon/cphalcon/security/advisories/GHSA-8jqh-95g6-7jpj
- https://github.com/phalcon/cphalcon/issues/17090
- https://github.com/phalcon/cphalcon/pull/17091
- https://github.com/phalcon/cphalcon/commit/ad53ab1b2e7ec59b3af92b0b37b8aaa099011137
- https://github.com/phalcon/cphalcon/releases/tag/v5.14.1
- https://github.com/phalcon/cphalcon
More phalcon vulnerabilities
- TI-2026-42773 Phalcon Volt compiler `join` filter compile-time PHP code injection (SSTI lead to RCE) CVSS 4.0CRITICAL 9.2
- TI-2026-41434 Phalcon: Catastrophic backtracking (ReDoS) in the default Phalcon Router route lead to remote unauthenticated DoS CVSS 4.0HIGH 8.7
Sources
- CVE-2026-54736 · CVE Program
- CVE-2026-54736 · NVD
- FIRST EPSS
- GHSA-8jqh-95g6-7jpj · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences