# CVE-2020-12656: Denial of service in n/a

> A memory leak in the Linux kernel's rpcsec_gss_krb5 implementation can lead to resource exhaustion, though exploitation requires privileged module loading.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 5 May 2020
- **Updated:** 4 Aug 2024
- **Also known as:** DEBIAN-CVE-2020-12656, GHSA-j42j-7596-mcr4, UBUNTU-CVE-2020-12656

## What is CVE-2020-12656?

CVE-2020-12656 is a medium-severity denial of service vulnerability in Canonical Ubuntu Linux, published on 5 May 2020. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

gss_mech_free in net/sunrpc/auth_gss/gss_mech_switch.c in the rpcsec_gss_krb5 implementation in the Linux kernel through 5.6.10 lacks certain domain_release calls, leading to a memory leak. Note: This was disputed with the assertion that the issue does not grant any access not already available. It is a problem that on unloading a specific kernel module some memory is leaked, but loading kernel modules is a privileged operation. A user could also write a kernel module to consume any amount of memory they like and load that replicating the effect of this bug

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2020-12656?

It affects 3 products.


Products: Canonical Ubuntu Linux, Linux kernel, Opensuse Leap.

## How do I fix CVE-2020-12656?

Apply the vendor's patch.

## Is CVE-2020-12656 being exploited?

There is no known exploitation of CVE-2020-12656 in the wild and no public exploit code.

## Other vulnerabilities in Canonical Ubuntu Linux

- [CVE-2020-11651](https://insights.sbomify.com/CVE-2020-11651/): SaltStack Salt Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2020-7247](https://insights.sbomify.com/CVE-2020-7247/): OpenSMTPD Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2019-16928](https://insights.sbomify.com/CVE-2019-16928/): Exim Out-of-bounds Write (critical 9.8, exploited in the wild)
- [CVE-2018-6789](https://insights.sbomify.com/CVE-2018-6789/): Exim Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2015-2590](https://insights.sbomify.com/CVE-2015-2590/): Oracle Java SE and Java SE Embedded Remote Code Execution (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-12656 and fix it if it is affected.

What it is: CVE-2020-12656 is a medium-severity denial of service vulnerability in Canonical Ubuntu Linux, published on 5 May 2020. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2020-12656 in the wild and no public exploit code.

Affected product: Canonical Ubuntu Linux. 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-2020-12656/ (Markdown: https://insights.sbomify.com/CVE-2020-12656/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-12656
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-12656
- OSV: https://osv.dev/vulnerability/CVE-2020-12656

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-12656/
Summaries are generated and may contain mistakes; the official description above is the record.