# guzzlehttp/guzzle: Dot-Only Cookie Domains Match All Hosts Advisory record · `GHSA-cwxw-98qj-8qjx` - **Identifiers:** `GHSA-cwxw-98qj-8qjx` · `CVE-2026-55767` · `PKSA-93qv-9n9h-6k6p` - **State:** Confirmed - **Severity:** CVSS 5.8 Medium - **Critical:** No - **Weakness (CWE):** [CWE-346](https://cwe.mitre.org/data/definitions/346.html) · [CWE-1286](https://cwe.mitre.org/data/definitions/1286.html) - **Tags:** [CWE-346](https://agentprime.io/advisories/tag/cwe-346.md) · [CWE-1286](https://agentprime.io/advisories/tag/cwe-1286.md) - **Published:** 19 Jun 2026 - **Updated:** 10 Sept 2026 - **Reviewed by a person:** No Published by the GitHub Advisory Database at 19 Jun 2026, 14:37 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. ## Affected packages - `guzzlehttp/guzzle` (Packagist): affected `<7.12.1`; fixed in `7.12.1` ## Machine-written summary Summary written by Claude Haiku from the source advisory. Not reviewed by a person. > The guzzlehttp/guzzle Packagist package, versions before 7.12.1, accepts cookies whose Domain attribute contains only dots (such as "Domain=.") and treats them as matching any request host. An attacker who controls an origin that an application requests through a shared cookie jar can set such a cookie and have Guzzle send it to unrelated hosts, which may enable cookie injection or session fixation depending on the downstream services. Upgrade to version 7.12.1 or later, which rejects dot-only Domain attributes; if upgrading is not possible, use separate cookie jars per trust boundary. 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 - 5.8 Medium, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N`, from CNA (GitHub_M) - **CISA KEV:** Not listed. - **EPSS:** 0.0021, the 11th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days. ## Timeline - 31 Oct 2026, 14:01 UTC: First seen by agentprime - 31 Oct 2026, 14:01 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-cwxw-98qj-8qjx) ## Sources - [GitHub Advisory Database: GHSA-cwxw-98qj-8qjx](https://github.com/advisories/GHSA-cwxw-98qj-8qjx) - [OSV: GHSA-cwxw-98qj-8qjx](https://osv.dev/vulnerability/GHSA-cwxw-98qj-8qjx) - - - - - - - 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: .