CVE-2025-4821 Affecting dnsdist package, versions <1.9.11-r0
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-ALPINE322-DNSDIST-13104386
- published27 Sept 2025
- disclosed18 Jun 2025
Introduced: 18 Jun 2025
CVE-2025-4821 (opens in a new tab)How to fix?
Upgrade Alpine:3.22 dnsdist to version 1.9.11-r0 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream dnsdist package and not the dnsdist package as distributed by Alpine.
See How to fix? for Alpine:3.22 relevant fixed versions and status.
Impact
Cloudflare quiche was discovered to be vulnerable to incorrect congestion window growth, which could cause it to send data at a rate faster than the path might actually support.
An unauthenticated remote attacker can exploit the vulnerability by first completing a handshake and initiating a congestion-controlled data transfer towards itself. Then, it could manipulate the victim's congestion control state by sending ACK frames covering a large range of packet numbers (including packet numbers that had never been sent); see RFC 9000 Section 19.3. The victim could grow the congestion window beyond typical expectations and allow more bytes in flight than the path might really support. In extreme cases, the window might grow beyond the limit of the internal variable's type, leading to an overflow panic.
Patches
quiche 0.24.4 is the earliest version containing the fix for this issue.