Cyber Resilience

CVE-2026-42009

Redhat Enterprise Linux 10.0 … 9.8

Published
18 May 2026
Modified
23 July 2026
CVSS Score v3.1 7.5
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS Score 0.013 69th percentile
Risk Priority 60 floored blend · peak EPSS

Summary

CVE-2026-42009 is a high-severity Undefined Behavior for Input to API (CWE-475) vulnerability in Redhat Enterprise Linux. Its CVSS base score is 7.5 (High).

Operationally, ranked in the top 31% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

A flaw was found in gnutls. A remote attacker could exploit an issue in the Datagram Transport Layer Security (DTLS) packet reordering logic. The comparator function, responsible for ordering DTLS packets by sequence numbers, did not correctly handle packets with…

more

duplicate sequence numbers. This could lead to unstable packet ordering or undefined behavior, resulting in a denial of service.

CWE(s)
CWE-475

Related Threats

CVEs Like This One

CVE-2026-42010Same product: Gnu Gnutls
CVE-2026-3833Same product: Gnu Gnutls
CVE-2026-3832Same product: Gnu Gnutls
CVE-2026-33845Same product: Gnu Gnutls
CVE-2025-32988Same product: Gnu Gnutls
CVE-2025-32989Same product: Gnu Gnutls
CVE-2025-32990Same product: Gnu Gnutls
CVE-2026-6846Same product: Redhat Enterprise Linux
CVE-2026-6844Same product: Redhat Enterprise Linux
CVE-2026-6845Same product: Redhat Enterprise Linux

Affected Assets

gnu
gnutls
all versions
redhat
hardened images
all versions
redhat
openshift container platform
4.0
redhat
enterprise linux
10.0, 10.2, 6.0, 7.0, 8.0
redhat
enterprise linux for els
10.2, 8.10, 9.8
redhat
enterprise linux for ibm z systems
10.2, 8.0_s390x, 9.0_s390x
redhat
enterprise linux for ibm z systems els
10.2, 8.10, 9.8
redhat
enterprise linux for power little endian
10.0, 10.2, 8.0_ppc64le, 9.0_ppc64le
redhat
enterprise linux for power little endian els
10.2, 8.10, 9.8
redhat
enterprise linux for eus
10.2, 9.8
+4 more product configuration(s) — see NVD for full list

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing and evaluation can discover calls that supply invalid control-parameter values before deployment.

SI-10 Information Input Validation good match

Validating inputs to API control parameters ensures only permitted values are supplied, structurally eliminating the source of undefined behavior.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices (coding standards, reviews, testing) directly prevent undefined behavior from invalid API inputs.

ID.RA-01 partial match
prevents

Vulnerability identification processes can discover and record this class of API-related weakness.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing can detect undefined behavior from invalid API inputs before deployment.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle includes API specification and validation that can prevent undefined behavior from invalid inputs.

A.8.26 Application security requirements partial match
prevents

Application security requirements can mandate explicit input validation and defined behavior for API parameters.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure system architecture principles can require defensive coding that eliminates undefined behavior in APIs.

A.8.28 Secure coding partial match
prevents

Secure coding directly addresses avoiding undefined behavior by enforcing defined inputs and error handling in APIs.

References