# CVE-2026-27932: joserfc PBES2 p2c Unbounded Iteration Count enables Denial of Service (DoS)

> An unauthenticated attacker can cause CPU exhaustion and Denial of Service in joserfc by sending a JWE token with an unbounded PBES2 iteration count.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 3 Mar 2026
- **Updated:** 4 Mar 2026
- **Also known as:** DEBIAN-CVE-2026-27932, GHSA-w5r5-m38g-f9f9, PYSEC-2026-2529, ROOT-APP-PYPI-CVE-2026-27932, UBUNTU-CVE-2026-27932, openSUSE-SU-2026:10293-1, openSUSE-SU-2026:20322-1

## What is CVE-2026-27932?

CVE-2026-27932 is a high-severity denial of service vulnerability in authlib joserfc, published on 3 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. In 1.6.2 and earlier, a resource exhaustion vulnerability in joserfc allows an unauthenticated attacker to cause a Denial of Service (DoS) via CPU exhaustion. When the library decrypts a JSON Web Encryption (JWE) token using Password-Based Encryption (PBES2) algorithms, it reads the p2c (PBES2 Count) parameter directly from the token's protected header. This parameter defines the number of iterations for the PBKDF2 key derivation function. Because joserfc does not validate or bound this value, an attacker can specify an extremely large iteration count (e.g., 2^31 - 1), forcing the server to expend massive CPU resources processing a single token. This vulnerability exists at the JWA layer and impacts all high-level JWE and JWT decryption interfaces if PBES2 algorithms are allowed by the application's policy.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-27932?

3 open source packages ship an affected version, including joserfc. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `joserfc` | PyPI | All versions | 1.6.3 |
| `joserfc` | PyPI | All versions | 1.6.3 |
| `joserfc` | PyPI | All versions | 1.6.3 |
| `python-joserfc` | openSUSE:Leap 16.0 | All versions | 1.1.0-bp160.2.1 |
| `python-joserfc` | openSUSE:Tumbleweed | All versions | 1.6.3-1.1 |

Products: Hsiaoming Joserfc.

## How do I fix CVE-2026-27932?

Upgrade joserfc to 1.6.3 or later.

## Is CVE-2026-27932 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27932 exists.

## Other vulnerabilities in authlib joserfc

- [CVE-2025-65015](https://insights.sbomify.com/CVE-2025-65015/): joserfc has Possible Uncontrolled Resource Consumption Vulnerability Triggered by Logging Arbitrarily Large JWT Token Payloads (critical 9.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-27932 and fix it if it is affected.

What it is: CVE-2026-27932 is a high-severity denial of service vulnerability in authlib joserfc, published on 3 Mar 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-2026-27932 exists.

Affected packages and fixed versions:
- joserfc (PyPI): affected all versions; fixed in 1.6.3
- joserfc (PyPI): affected all versions; fixed in 1.6.3
- joserfc (PyPI): affected all versions; fixed in 1.6.3

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-2026-27932/ (Markdown: https://insights.sbomify.com/CVE-2026-27932/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-27932
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27932
- OSV: https://osv.dev/vulnerability/CVE-2026-27932

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-27932/
Summaries are generated and may contain mistakes; the official description above is the record.