# Symfony: Unbounded Recursion in the YAML Inline Lexer Lets a Single Document Crash the Process Advisory record · `GHSA-2v3c-qxhr-7vpv` - **Identifiers:** `GHSA-2v3c-qxhr-7vpv` · `CVE-2026-109413` · `PKSA-fyjn-dgwp-4tt3` · `PKSA-xz3r-9gp4-4m1z` - **State:** Confirmed - **Severity:** CVSS 8.7 High - **Critical:** No - **Weakness (CWE):** [CWE-674](https://cwe.mitre.org/data/definitions/674.html) - **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md) - **Published:** 27 Oct 2026 - **Updated:** 27 Oct 2026 - **Reviewed by a person:** No Published by the GitHub Advisory Database at 27 Oct 2026, 19:01 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. ## Affected packages - `symfony/symfony` (Packagist): affected `>=2.0.0, <5.4.54 || >=6.0.0, <6.4.45 || >=7.0.0, <7.4.18 || >=8.0.0, <8.1.6`; fixed in `5.4.54`, `6.4.45`, `7.4.18`, `8.1.6` - `symfony/yaml` (Packagist): affected `>=2.0.0, <5.4.54 || >=6.0.0, <6.4.45 || >=7.0.0, <7.4.18 || >=8.0.0, <8.1.6`; fixed in `5.4.54`, `6.4.45`, `7.4.18`, `8.1.6` ## Machine-written summary Summary written by Claude Haiku from the source advisory. Not reviewed by a person. > Symfony's symfony/symfony and symfony/yaml packages are affected in versions before 5.4.54, from 6.0.0 before 6.4.45, from 7.0.0 before 7.4.18, and from 8.0.0 before 8.1.6. An attacker can supply a YAML document with deeply nested inline collections, which exhausts the stack in the inline lexer and crashes the process or ends the request with a fatal error. Any code parsing untrusted YAML is affected, and no authentication is needed. Upgrade symfony/symfony and symfony/yaml to 5.4.54, 6.4.45, 7.4.18, or 8.1.6 according to your branch. 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 - 8.7 High, CVSS 4.0: `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`, from CNA (Checkmarx) - **CISA KEV:** Not listed. - **EPSS:** 0.0040, the 33rd 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-2v3c-qxhr-7vpv) ## Sources - [GitHub Advisory Database: GHSA-2v3c-qxhr-7vpv](https://github.com/advisories/GHSA-2v3c-qxhr-7vpv) - [OSV: GHSA-2v3c-qxhr-7vpv](https://osv.dev/vulnerability/GHSA-2v3c-qxhr-7vpv) - - - - - - - - - - - - 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 (), 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: - In a browser: reads your lockfile in the browser, never uploading it. - Whether it touches your code, with file and line: the Claude Code plugin, - As JSON: , or `POST https://api.agentprime.io/v1/match` with your packages () --- The web page: . Everything for agents: .