# CVE-2026-3099: Libsoup: libsoup: authentication bypass via digest authentication replay attack

> Remote attackers can bypass authentication in libsoup by replaying captured digest headers, gaining unauthorized access to protected resources.

- **Severity:** Medium 5.8 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 12 Mar 2026
- **Updated:** 1 May 2026
- **Also known as:** AZL-80415, DEBIAN-CVE-2026-3099, GHSA-hrf3-6c7v-5628, ROOT-OS-DEBIAN-12-CVE-2026-3099, ROOT-OS-DEBIAN-13-CVE-2026-3099, UBUNTU-CVE-2026-3099

## What is CVE-2026-3099?

CVE-2026-3099 is a medium-severity authentication bypass vulnerability in Redhat Enterprise Linux, published on 12 Mar 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

A flaw was found in Libsoup. The server-side digest authentication implementation in the SoupAuthDomainDigest class does not properly track issued nonces or enforce the required incrementing nonce-count (nc) attribute. This vulnerability allows a remote attacker to capture a single valid authentication header and replay it repeatedly. Consequently, the attacker can bypass authentication and gain unauthorized access to protected resources, impersonating the legitimate user.

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

## Which versions are affected by CVE-2026-3099?

It affects 2 products.


Products: Gnome Libsoup, Redhat Enterprise Linux.

## How do I fix CVE-2026-3099?

Apply the vendor's patch.

## Is CVE-2026-3099 being exploited?

There is no known exploitation of CVE-2026-3099 in the wild and no public exploit code.

## Other vulnerabilities in Redhat Enterprise Linux

- [CVE-2026-102556](https://insights.sbomify.com/CVE-2026-102556/): Libsoup: libsoup: heap buffer overflow from websocket pong signal type confusion (high 8.6)
- [CVE-2026-102557](https://insights.sbomify.com/CVE-2026-102557/): Libsoup: libsoup: heap buffer overflow during websocket message reassembly (high 8.6)
- [CVE-2026-102558](https://insights.sbomify.com/CVE-2026-102558/): Libsoup: libsoup: heap buffer overflow during websocket receive-buffer growth (high 8.6)
- [CVE-2026-102559](https://insights.sbomify.com/CVE-2026-102559/): Libsoup: libsoup: heap buffer overflow during websocket client-frame masking (high 8.6)
- [CVE-2026-102560](https://insights.sbomify.com/CVE-2026-102560/): Libsoup: libsoup: heap buffer overflow during outgoing permessage-deflate buffer growth (high 8.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-3099 and fix it if it is affected.

What it is: CVE-2026-3099 is a medium-severity authentication bypass vulnerability in Redhat Enterprise Linux, published on 12 Mar 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-3099 in the wild and no public exploit code.

Affected product: Redhat Enterprise 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-2026-3099/ (Markdown: https://insights.sbomify.com/CVE-2026-3099/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-3099
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-3099
- OSV: https://osv.dev/vulnerability/CVE-2026-3099

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-3099/
Summaries are generated and may contain mistakes; the official description above is the record.