CVE-2026-633859.2CriticalCWE-444

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

libevent

Affected: libevent · Exploitation: possible (1 to 10%)

Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.

1.3%probability of exploitation in the next 30 days

70th percentile

050100

Higher than 70% of scored CVEs

9.2CriticalCVSS 4.0

LowMediumHighCrit.

DescriptionCVE.org

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.

Affected products1

From the CVE record. A product or version that is not listed is unknown, not unaffected.

libevent · libevent>= 2.2.0-alpha, < 2.2.2-alpha; < 2.1.13

On the Atlas

Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.

Open the Atlas

Exploitation: Possible (1 to 10%). EPSS between 1% and 10%.
CISA KEV: Not listed
Public check: No public nuclei template
Weakness: Inconsistent Interpretation of HTTP Requests · Injection and Smuggling
Vendor: libevent
Published: August 2026
Band: Possible (1 to 10%), August 2026

CoverageNo articles yet

No CyberSIXT article names CVE-2026-63385 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.