# CVE-2026-77205: Denial of Service via sending bogus X.509 certificates

> Attackers can lock out legitimate peers by sending bogus certificates that persist in the cache, causing denial of service in FIPS mode.

- **Severity:** Low 3.7 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 13 Oct 2026
- **Updated:** 16 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-77205, GHSA-7m29-c28j-rg7h, UBUNTU-CVE-2026-77205

## What is CVE-2026-77205?

CVE-2026-77205 is a low-severity denial of service vulnerability in The Libreswan Project libreswan, published on 13 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Libreswan in FIPS mode has a vulnerability where badly formed received certificates are rejected, but not deleted from the NSS cache. As a result, any real certificates with the same serial number are rejected as well. This can be abused to lock out legitimate peers from connecting. The add_decoded_cert() function missed a call to CERT_DestroyCertificate() due to an incorrect fix for CVE-2026-14957. Sending bogus certificates with new serial numbers could prevent the real certificates with those serial numbers from connecting until the service has restarted.

Weakness: CWE-772 (Missing Release of Resource after Effective Lifetime)

## Which versions are affected by CVE-2026-77205?


## How do I fix CVE-2026-77205?

Apply the vendor's patch.

## Is CVE-2026-77205 being exploited?

There is no known exploitation of CVE-2026-77205 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77205 and fix it if it is affected.

What it is: CVE-2026-77205 is a low-severity denial of service vulnerability in The Libreswan Project libreswan, published on 13 Oct 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-2026-77205 in the wild and no public exploit code.

Affected product: The Libreswan Project libreswan. 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-2026-77205/ (Markdown: https://insights.sbomify.com/CVE-2026-77205/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77205
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77205
- OSV: https://osv.dev/vulnerability/CVE-2026-77205

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-77205/
Summaries are generated and may contain mistakes; the official description above is the record.