# CVE-2026-63385: Libevent: HTTP header handling bugs create risk of access control bypass.

> Attackers can bypass access controls or inject headers in applications using Libevent due to URI decoding and header parsing flaws.

- **Severity:** Critical 9.2 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:L/SI:L/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 20 Aug 2026
- **Updated:** 21 Aug 2026
- **Also known as:** AZL-96897, AZL-96947, AZL-97539, AZL-97566, BELL-CVE-2026-63385, DEBIAN-CVE-2026-63385, ECHO-7ffd-12b3-6870, GHSA-jcwh-pvf2-73p2, RHSA-2026:70254, ROOT-OS-DEBIAN-11-CVE-2026-63385, UBUNTU-CVE-2026-63385

## What is CVE-2026-63385?

CVE-2026-63385 is a critical vulnerability in libevent, published on 20 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has two HTTP parsing weaknesses in http.c. evhttp_decode_uri_internal decodes percent-encoded %00 bytes into literal NUL characters, which can cause downstream C string operations to truncate a path and bypass validation performed on a different representation. evhttp_header_is_valid_value also accepts obsolete line folding in header values containing carriage return or line feed characters, allowing a proxy and libevent to interpret headers differently and enabling header injection or access control bypass. The CRLF header acceptance is fixed in versions 2.1.13 and 2.2.2-alpha, but the reviewed patches do not clearly remediate the URI NUL-truncation condition.

Weakness: CWE-444 (Inconsistent Interpretation of HTTP Requests)

## Which versions are affected by CVE-2026-63385?


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `libevent` | Red Hat:hummingbird:1 | All versions | 0:2.1.13-1.hum1 |
| `libevent-devel` | Red Hat:hummingbird:1 | All versions | 0:2.1.13-1.hum1 |
| `libevent-doc` | Red Hat:hummingbird:1 | All versions | 0:2.1.13-1.hum1 |

## How do I fix CVE-2026-63385?

Apply the vendor's patch.

## Is CVE-2026-63385 being exploited?

There is no known exploitation of CVE-2026-63385 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-63385 and fix it if it is affected.

What it is: CVE-2026-63385 is a critical vulnerability in libevent, published on 20 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-2026-63385 in the wild and no public exploit code.

Affected product: libevent. 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-2026-63385/ (Markdown: https://insights.sbomify.com/CVE-2026-63385/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-63385
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-63385
- OSV: https://osv.dev/vulnerability/CVE-2026-63385

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-63385/
Summaries are generated and may contain mistakes; the official description above is the record.