# gosaml2 CBC Padding Panic — Unauthenticated Process Crash

Advisory record · `GHSA-hwqm-qvj9-4jr2`

- **Identifiers:** `GHSA-hwqm-qvj9-4jr2` · `GO-2026-4760`
- **State:** Confirmed
- **Severity:** CVSS 4.0, no score published
- **Critical:** No
- **Weakness (CWE):** [CWE-129](https://cwe.mitre.org/data/definitions/129.html)
- **Tags:** [CWE-129](https://agentprime.io/advisories/tag/cwe-129.md)
- **Published:** 18 Mar 2026
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 18 Mar 2026, 20:19 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `github.com/russellhaering/gosaml2` (Go): affected `<0.11.0`; fixed in `0.11.0`

## Machine-written summary

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

> Versions of gosaml2 before 0.11.0 panic when decrypting an AES-CBC encrypted assertion whose decrypted plaintext is all zero bytes. An unauthenticated attacker who knows the service provider's public RSA key, which is published in SAML metadata, can send one crafted HTTP POST to the assertion consumer endpoint, crashing the process or the request goroutine, and can repeat it. Upgrade to gosaml2 0.11.0 or later.

Written 1 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

- Score not published, 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 GitHub Advisory Database

- **CISA KEV:** Not listed.
- **EPSS:** No score.

## Timeline

- 31 Oct 2026, 14:14 UTC: First seen by agentprime
- 31 Oct 2026, 14:14 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-hwqm-qvj9-4jr2)

## Sources

- [GitHub Advisory Database: GHSA-hwqm-qvj9-4jr2](https://github.com/advisories/GHSA-hwqm-qvj9-4jr2)
- [OSV: GHSA-hwqm-qvj9-4jr2](https://osv.dev/vulnerability/GHSA-hwqm-qvj9-4jr2)
- <https://github.com/russellhaering/gosaml2/security/advisories/GHSA-hwqm-qvj9-4jr2>
- <https://github.com/russellhaering/gosaml2>

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-hwqm-qvj9-4jr2>, 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-hwqm-qvj9-4jr2/>. Everything for agents: <https://agentprime.io/llms.txt>.