High [CVE-2026-63387] Off-by-one stack buffer overflow leading to denial of service or data corruption
This high-severity Red Hat Linux advisory covers CVE-2026-63387 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7.
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Summary
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.
A remote attacker could send a specially crafted DNS server response, which may lead to a crash or corruption of the process, resulting in a denial of service or potential information disclosure and integrity impact. Red Hat severity: Important — CVSS 8.6 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H).
Weakness: CWE-787. Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9; Red Hat Hardened Images; Red Hat OpenShift Container Platform 4.
Red Hat does not currently list a fixing RHSA for this CVE.
Affected products named by the advisory: Red Hat package: libevent2.
- < 2.1.13
- < 2.2.2-alpha
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
- 2.1.13
- 2.2.2
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
Mitigation
Upgrade to a fixed release: 2.1.13, 2.2.2. That is the remediation for this advisory.
The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
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