# Grav: Non constant time nonce comparison in Utils::verifyNonce() used for CSRF protection

Advisory record · `GHSA-38p6-h87p-r4cg`

- **Identifiers:** `GHSA-38p6-h87p-r4cg` · `CVE-2026-72701` · `PKSA-xzd7-91fp-yh97`
- **State:** Confirmed
- **Severity:** CVSS 6.3 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-208](https://cwe.mitre.org/data/definitions/208.html)
- **Tags:** [CWE-208](https://agentprime.io/advisories/tag/cwe-208.md)
- **Published:** 17 Sept 2026
- **Updated:** 26 Oct 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 17 Sept 2026, 20:25 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `getgrav/grav` (Packagist): affected `<2.0.16`; fixed in `2.0.16`

## Machine-written summary

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

> The Grav CMS package getgrav/grav, versions before 2.0.16, has a non-constant-time comparison in Utils::verifyNonce(), which is used for CSRF nonce checks; the source reports it uses PHP's === operator rather than hash_equals(). An attacker who can send many requests and precisely measure response timing might in principle recover a valid nonce byte by byte, but the source says the timing signal is very small and that it did not demonstrate a practical remote attack. The fix is to upgrade to version 2.0.16.

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

- 6.3 Medium, CVSS 4.0: `CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N`, from CNA (VulnCheck)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0022, the 12th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 13:53 UTC: First seen by agentprime
- 31 Oct 2026, 13:53 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-38p6-h87p-r4cg)

## Sources

- [GitHub Advisory Database: GHSA-38p6-h87p-r4cg](https://github.com/advisories/GHSA-38p6-h87p-r4cg)
- [OSV: GHSA-38p6-h87p-r4cg](https://osv.dev/vulnerability/GHSA-38p6-h87p-r4cg)
- <https://github.com/getgrav/grav/security/advisories/GHSA-38p6-h87p-r4cg>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-72701>
- <https://github.com/getgrav/grav/commit/a076b9073abc51c1df924529d65773e44950c5c4>
- <https://github.com/getgrav/grav>
- <https://github.com/getgrav/grav/releases/tag/2.0.16>
- <https://www.vulncheck.com/advisories/grav-cms-before-timing-attack-via-verifynonce>

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-38p6-h87p-r4cg>, 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-38p6-h87p-r4cg/>. Everything for agents: <https://agentprime.io/llms.txt>.