Quick answers
- Is CVE-2026-63383 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-63383 being exploited in the wild.
- How severe is CVE-2026-63383?
- Informational severity, published 20 August 2026.
- Which products and versions are affected?
- Libevent prior to 2.1.13 and prior to 2.2.2-alpha.
- Is there a fix for CVE-2026-63383?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-63383 attacked?
- It is attacked over the network.
- Am I affected by CVE-2026-63383?
- Check whether you run Libevent at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability is an out-of-bounds read in the decode_tag_internal function in event_tagging.c. The function calls evbuffer_pullup with a calculated window size (at most 6 bytes) but then iterates over the full logical buffer length, causing it to read past the pullup boundary. A fragmented evbuffer containing a six-byte malformed tag can trigger out-of-bounds memory access. The attack vector is network-based: an attacker sends a specially crafted RPC message to a service using Libevent. The fix, applied in versions 2.1.13 and 2.2.2-alpha, constrains the iteration to the actual pullup length.
Affected products
- Libevent Libevent prior to 2.1.13 and prior to 2.2.2-alpha
Timeline
- 2026-08-20: disclosed