# CVE-2026-59099: Apereo CAS 7.3.0 < 8.0.0-RC6 - AES-GCM Nonce Reuse Information Disclosure

> Remote attackers can decrypt webflow conversation state by exploiting AES-GCM nonce reuse, potentially bypassing authentication flows.

- **Severity:** Critical 9.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 2 Jul 2026
- **Updated:** 14 Jul 2026
- **Also known as:** GHSA-phqw-pwxm-86gq

## What is CVE-2026-59099?

CVE-2026-59099 is a critical vulnerability in apereo cas, published on 2 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Apereo CAS 7.3.0 before 8.0.0-RC6 contains a cryptographic vulnerability that allows remote unauthenticated attackers to recover plaintext conversation state by exploiting AES-GCM initialization vector reuse across the server lifetime. Attackers can collect multiple client-side webflow execution tokens from the unauthenticated login page and perform known-plaintext analysis to decrypt the webflow conversation state due to keystream reuse caused by a fixed all-zero IV paired with the same encryption key.

Weakness: CWE-323 (Reusing a Nonce, Key Pair in Encryption)

## Which versions are affected by CVE-2026-59099?


## How do I fix CVE-2026-59099?

No fix has been published for CVE-2026-59099 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-59099 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59099 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-59099 and fix it if it is affected.

What it is: CVE-2026-59099 is a critical vulnerability in apereo cas, published on 2 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59099 exists.

Affected product: apereo cas. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-59099/ (Markdown: https://insights.sbomify.com/CVE-2026-59099/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-59099
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-59099
- OSV: https://osv.dev/vulnerability/CVE-2026-59099

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-59099/
Summaries are generated and may contain mistakes; the official description above is the record.