# Flask vulnerable to possible disclosure of permanent session cookie due to missing Vary: Cookie header Advisory record · `GHSA-m2qf-hxjv-5gpq` - **Identifiers:** `GHSA-m2qf-hxjv-5gpq` · `CVE-2023-30861` · `PYSEC-2023-62` - **State:** Confirmed - **Severity:** CVSS 7.5 High - **Critical:** No - **Weakness (CWE):** [CWE-539](https://cwe.mitre.org/data/definitions/539.html) - **Tags:** [CWE-539](https://agentprime.io/advisories/tag/cwe-539.md) - **Published:** 1 May 2023 - **Updated:** 10 Sept 2026 - **Reviewed by a person:** No Published by the GitHub Advisory Database at 1 May 2023, 19:22 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. ## Affected packages - `flask` (PyPI): affected `>=2.3.0, <2.3.2 || <2.2.5`; fixed in `2.3.2`, `2.2.5` ## Machine-written summary Summary written by Claude Haiku from the source advisory. Not reviewed by a person. > Flask versions from 2.2.5 (exclusive) up to 2.3.0 (exclusive), and from 2.3.0 up to 2.3.2 (exclusive), are affected. If a caching proxy sits in front of an application that sets session.permanent to True, never accesses the session during a request, keeps the default session refresh, and sets no private Cache-Control header, a response carrying one client's session cookie can be cached and sent to other clients. Upgrade to Flask 2.2.5 or 2.3.2. The source gives no workaround beyond upgrading. Written 5 Nov 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 - 7.5 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`, from CNA (GitHub_M) - **CISA KEV:** Not listed. - **EPSS:** 0.013, the 69th percentile, on 6 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days. ## Timeline - 31 Oct 2026, 14:36 UTC: First seen by agentprime - 31 Oct 2026, 14:36 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-m2qf-hxjv-5gpq) ## Sources - [GitHub Advisory Database: GHSA-m2qf-hxjv-5gpq](https://github.com/advisories/GHSA-m2qf-hxjv-5gpq) - [OSV: GHSA-m2qf-hxjv-5gpq](https://osv.dev/vulnerability/GHSA-m2qf-hxjv-5gpq) - - - - - - - - - - - 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: .