CVE-2026-63385
Libevent HTTP parsing flaws allow header injection and NUL-based URI truncation, enabling access bypass or RCE.
Is CVE-2026-63385 being exploited?
Not confirmed. CVE-2026-63385 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.40% probability of exploitation in the next 30 days.
How severe is CVE-2026-63385?
CVE-2026-63385 is rated Critical with a CVSS score of 9.2. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-63385?
Yes. A fix has been recorded for CVE-2026-63385. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-63385 affect?
CVE-2026-63385 affects libevent < 2.1.13, libevent < 2.2.2-alpha, Applications embedding libevent (proxies, daemons, network services). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-63385?
Upgrade to libevent >=2.1.13 or >=2.2.2-alpha, audit URI handling, and apply WAF/proxy mitigations.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Crafted HTTP requests can inject headers or use percent-encoded %00 to truncate URIs, causing access-control bypass, header injection, or remote code execution in apps using libevent.
Immediate action required
- affected>= 2.2.0-alpha and < 2.2.2-alpha
- affected< 2.1.13
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.