CVE-2026-40691 The advisory has been revoked - it doesn't affect any version of package rhcos (opens in a new tab)
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-RHEL9-RHCOS-18248816
- published23 Jul 2026
- disclosed22 Jul 2026
Introduced: 22 Jul 2026
CVE-2026-40691 (opens in a new tab)Amendment
The Red Hat security team deemed this advisory irrelevant for RHEL:9.
NVD Description
Note: Versions mentioned in the description apply only to the upstream rhcos package and not the rhcos package as distributed by RHEL.
In Unbound 1.9.0 up to and including 1.25.1, when a DNSCrypt query is received over TCP, the routine that encrypts the reply in place fails to bound the reply length against the destination buffer size. The size clamp that protects the UDP path is not applied on the TCP path, so a reply larger than 65504 bytes is shifted forward by 48 bytes inside a buffer of capacity equal to 'msg-buffer-size', writing past the end of the heap allocation. A single malicious encrypted query crashes the resolver and lead to denial of service. This vulnerability needs Unbound to be compiled with DNSCrypt support ('--enable-dnscrypt') and the 'dnscrypt:' clause to be configured and enabled for the listening interfaces.