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High, CVSS 8.2amended

Phalcon: Non-constant-time HMAC verification in Encryption\Crypt::decrypt (timing side-channel)

CVE-2026-54736GHSA-8jqh-95g6-7jpj

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (phalcon/cphalcon 5.14.1), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
8.2 · CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N · score source
EPSS
  • CVE-2026-54736: 0.18% estimated exploitation activity in the next 30 days; percentile 7.66 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary Phalcon\Encryption\Crypt provides authenticated encryption: when useSigning is enabled (the default), encrypt() appends an HMAC tag and decrypt() verifies it before returning the plaintext. The verification compares the attacker-supplied tag against the freshly computed HMAC using PHP/Zephir identity comparison (!==), which the Zephir compiler lowers to !ZEPHIRISIDENTICAL(...) — a byte-wise memcmp that returns early on the first differing byte. The comparison time therefore depends on how many leading bytes of the supplied tag are correct, a classic MAC-verification timing side-channel. Every other secret/MAC comparison in the framework uses the constant-time hashequals() (zephirhashequals) — the CSRF token check (Security::checkToken) and the JWT signature check (Signer\Hmac::verify); Crypt::decrypt is the lone deviation. Details Vulnerable code phalcon/Encryption/Crypt.zep:246 (Zephir source): Generated C -- ext/phalcon/encryption/crypt.zep.c:364-367: ZEPHIRISIDENTICAL --…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-8jqh-95g6-7jpj

  2. Revision 2 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 1 · created ·

    Published from osv record GHSA-8jqh-95g6-7jpj

Agent brief

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# Patch Next advisory brief: CVE-2026-54736

Advisory: Phalcon: Non-constant-time HMAC verification in `Encryption\Crypt::decrypt` (timing side-channel)
IDs: CVE-2026-54736, GHSA-8jqh-95g6-7jpj
Record: https://patchnext.com/advisories/cve-2026-54736 (revision 3, source checked 26 Oct 2026, 14:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: phalcon/cphalcon 5.14.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist phalcon/cphalcon: affected <= 5.14.0; fixed in 5.14.1

## Suggested inspection (read-only)
- Packagist phalcon/cphalcon: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on phalcon/cphalcon.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-8jqh-95g6-7jpj (OSV record GHSA-8jqh-95g6-7jpj lists affected ranges: Packagist phalcon/cphalcon >=0 <5.14.1 (fixed))
- Verified: https://github.com/advisories/GHSA-8jqh-95g6-7jpj (GitHub-reviewed advisory GHSA-8jqh-95g6-7jpj lists affected ranges: Packagist phalcon/cphalcon >=0 <=5.14.0)

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