# CVE-2026-6791: Potential stack-based buffer clash during tilde expansion in wordexp

> An attacker can cause a denial of service via stack exhaustion in glibc's wordexp function by providing an excessively long username during tilde expansion.

- **Severity:** Medium 6.6 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:L/SA:H/E:U`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 10 Aug 2026
- **Updated:** 12 Aug 2026
- **Also known as:** AZL-95492, BELL-CVE-2026-6791, DEBIAN-CVE-2026-6791, ECHO-9658-3093-2999, GHSA-ch73-g8qv-r6r5, MINI-4xxf-44hj-m8hg, UBUNTU-CVE-2026-6791

## What is CVE-2026-6791?

CVE-2026-6791 is a medium-severity denial of service vulnerability in The GNU C Library glibc, published on 10 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

When expanding paths that begin with a tilde (~) followed by a username, the internal parse_tilde function extracts the username to determine the user's home directory.  The implementation allocates memory for this username directly on the stack using the strndupa macro. Because the size of this allocation was determined by the length of the user-supplied input without any bounds checks, passing an excessively long username e.g. thousands of characters, forces the thread to exhaust its stack space. Thus if an application passes untrusted, attacker-controlled input to the wordexp function, an attacker can trigger a stack clash.

Weakness: CWE-121 (Stack-based Buffer Overflow)

## Which versions are affected by CVE-2026-6791?


## How do I fix CVE-2026-6791?

Apply the vendor's patch.

## Is CVE-2026-6791 being exploited?

There is no known exploitation of CVE-2026-6791 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-6791 and fix it if it is affected.

What it is: CVE-2026-6791 is a medium-severity denial of service vulnerability in The GNU C Library glibc, published on 10 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-6791 in the wild and no public exploit code.

Affected product: The GNU C Library glibc. 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-2026-6791/ (Markdown: https://insights.sbomify.com/CVE-2026-6791/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-6791
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-6791
- OSV: https://osv.dev/vulnerability/CVE-2026-6791

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-6791/
Summaries are generated and may contain mistakes; the official description above is the record.