CVE-2026-33630: c-ares Double Free

Vulnerability summary

CVE-2026-33630 is a high (CVSS 7.5) Double Free vulnerability in c-ares. EPSS estimates a 0.84% chance of exploitation in the next 30 days, higher than 57.5% of scored vulnerabilities.

Timeline

1. 03-09-2026
   PublishedVulnerability first disclosed.
2. 05-09-2026
   Last modifiedVulnerability information updated.

Description

c-ares is an asynchronous resolver library. From ver 1.32.3 until 1.34.7, a use-after-free / double-free in c-ares' query-completion handling. The same flaw — a query's callback being invoked while the query is still linked in the channel's internal lookup structures — is present at multiple points in the resend/finish path (timeout handling, response handling, and query dispatch). If the query, or for ares_getaddrinfo() the owning host_query, is freed as a side effect of that callback, it is then accessed and/or freed a second time. This vulnerability is fixed in ver 1.34.7.

• CWE-415Double FreeThe product calls free() twice on the same memory address.
• CWE-416Use After FreeThe product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.