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CVE-2026-63387

CVE-2026-63387 · Libevent: Off-by-one stack buffer overflow in dnsname_to_labels via crafted DNS server response

This page contains facts from public vulnerability sources. Check the original advisory before updating.

Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has an off-by-one stack buffer overflow in evdns.c when dnsname_to_labels formats a name-bearing DNS record at the end of the 64 KB stack buffer allocated by evdns_server_request_format_response. The final-label check permits j plus label_len plus one to equal buf_len, after which the terminating null byte is written to buf[buf_len]. A crafted DNS server response containing PTR, CNAME, MX, NS, or SOA data can trigger the one-byte out-of-bounds write and crash or corrupt the process. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.

CVSS 7.0 · High · EPSS 0.4% · Fix available

Published
Updated

Stack: system

Affected products and versions

  • libevent

    Versions
    • >= 2.2.0-alpha, < 2.2.2-alpha: Affected
    • < 2.1.13: Affected

    No fix published

  • libevent Debian:12

    Versions
    • 2.1.12-stable-8
    Affected ranges
    • ECOSYSTEM: < 2.1.12-stable-8+deb12u1

    Update to 2.1.12-stable-8+deb12u1

  • libevent Debian:13

    Versions
    • 2.1.12-stable-10
    Affected ranges
    • ECOSYSTEM: < 2.1.13-stable-1~deb13u1

    Update to 2.1.13-stable-1~deb13u1

  • libevent Debian:14

    Versions
    • 2.1.12-stable-10
    • 2.1.13-stable-1~deb13u1
    Affected ranges
    • ECOSYSTEM: < 2.1.13-stable-1

    Update to 2.1.13-stable-1

  • libevent Ubuntu:Pro:14.04:LTS

    Versions
    • 2.0.21-stable-1
    • 2.0.21-stable-1ubuntu1
    • 2.0.21-stable-1ubuntu1.14.04.1
    • 2.0.21-stable-1ubuntu1.14.04.2
    • 2.0.21-stable-1ubuntu1.14.04.2+esm1
    • 2.0.21-stable-1ubuntu1.14.04.2+esm2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • libevent Ubuntu:Pro:16.04:LTS

    Versions
    • 2.0.21-stable-2
    • 2.0.21-stable-2ubuntu0.16.04.1
    • 2.0.21-stable-2ubuntu0.16.04.1+esm1
    • 2.0.21-stable-2ubuntu0.16.04.1+esm2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • libevent Ubuntu:Pro:18.04:LTS

    Versions
    • 2.1.8-stable-4
    • 2.1.8-stable-4build1
    • 2.1.8-stable-4ubuntu0.1~esm1
    • 2.1.8-stable-4ubuntu0.1~esm2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • libevent Ubuntu:Pro:20.04:LTS

    Versions
    • 2.1.8-stable-4build1
    • 2.1.11-stable-1~exp0
    • 2.1.11-stable-1
    • 2.1.11-stable-1ubuntu0.1~esm1
    • 2.1.11-stable-1ubuntu0.1~esm2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • libevent Ubuntu:22.04:LTS

    Versions
    • 2.1.12-stable-1
    • 2.1.12-stable-1build1
    • 2.1.12-stable-1build2
    • 2.1.12-stable-1build3
    • 2.1.12-stable-1ubuntu0.1
    • 2.1.12-stable-1ubuntu0.2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • libevent Ubuntu:24.04:LTS

    Versions
    • 2.1.12-stable-9
    • 2.1.12-stable-9ubuntu2
    • 2.1.12-stable-9ubuntu2.1
    • 2.1.12-stable-9ubuntu2.2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • libevent Ubuntu:26.04:LTS

    Versions
    • 2.1.12-stable-10build1
    • 2.1.12-stable-10build2
    • 2.1.12-stable-10ubuntu0.1
    Affected ranges
    • ECOSYSTEM: < 2.1.12-stable-10ubuntu0.2

    Update to 2.1.12-stable-10ubuntu0.2

Original sources

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