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

Advisory record · `GHSA-8jqh-95g6-7jpj`

- **Identifiers:** `GHSA-8jqh-95g6-7jpj` · `CVE-2026-54736` · `PKSA-65xj-m5g6-56k1`
- **State:** Confirmed
- **Severity:** CVSS 8.2 High
- **Critical:** No
- **Weakness (CWE):** [CWE-208](https://cwe.mitre.org/data/definitions/208.html) · [CWE-347](https://cwe.mitre.org/data/definitions/347.html)
- **Tags:** [Weak cryptography or TLS](https://agentprime.io/advisories/tag/weak-crypto.md) · [CWE-208](https://agentprime.io/advisories/tag/cwe-208.md)
- **Published:** 28 Aug 2026
- **Updated:** 28 Aug 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 28 Aug 2026, 16:01 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `phalcon/cphalcon` (Packagist): affected `<5.14.1`; fixed in `5.14.1`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> Phalcon's \`Crypt::decrypt\` in the Packagist package phalcon/cphalcon, versions before 5.14.1, checks the HMAC tag with a comparison whose timing depends on how many leading bytes match, creating a timing side-channel. An attacker who can submit ciphertexts and measure response times could potentially forge a valid tag and defeat the integrity check, though the source notes there is no confidentiality break on its own. Upgrade to 5.14.1, which fixes the issue.

Written 31 Oct 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 8.2 High, CVSS 4.0: `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`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0018, the 7th percentile, on 6 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:07 UTC: First seen by agentprime
- 31 Oct 2026, 14:07 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-8jqh-95g6-7jpj)

## Sources

- [GitHub Advisory Database: GHSA-8jqh-95g6-7jpj](https://github.com/advisories/GHSA-8jqh-95g6-7jpj)
- [OSV: GHSA-8jqh-95g6-7jpj](https://osv.dev/vulnerability/GHSA-8jqh-95g6-7jpj)
- <https://github.com/phalcon/cphalcon/security/advisories/GHSA-8jqh-95g6-7jpj>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-54736>
- <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>
- <https://github.com/phalcon/cphalcon/releases/tag/v5.14.1>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-8jqh-95g6-7jpj>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-8jqh-95g6-7jpj/>. Everything for agents: <https://agentprime.io/llms.txt>.