CVE-2026-5673

MediumPublic PoC

Published: 06 April 2026

Published

06 April 2026

Modified

01 May 2026

KEV Added

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Patch

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CVSS Score 5.6 CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:H

EPSS Score 0.0001 0.3th percentile

Risk Priority 11 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-5673 is a medium-severity Out-of-bounds Read (CWE-125) vulnerability in Redhat Enterprise Linux. Its CVSS base score is 5.6 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Malicious File (T1204.002); ranked at the 0.3th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

The strongest mitigations our analysis identified are NIST 800-53 SI-16 (Memory Protection) and SI-2 (Flaw Remediation).

Threat & Defense at a Glance

What attackers do: exploitation maps to Malicious File (T1204.002) and 1 other technique. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-2 Flaw Remediation good match

prevent

SI-2 requires timely remediation of flaws like the heap-based out-of-bounds read in libtheora by applying patches referenced in the advisories.

SI-16 Memory Protection good match

prevent

SI-16 implements memory protections such as ASLR and stack canaries that directly mitigate heap out-of-bounds read exploits leading to crashes or leaks.

SI-10 Information Input Validation partial match

prevent

SI-10 enforces validation of AVI file inputs to block specially crafted files with truncated headers before they reach the vulnerable parser.

MITRE ATT&CK Enterprise TechniquesAI

T1204.002 Malicious File Execution

An adversary may rely upon a user opening a malicious file in order to gain execution.

attack.mitre.org →

T1499.004 Application or System Exploitation Impact

Adversaries may exploit software vulnerabilities that can cause an application or system to crash and deny availability to users.

attack.mitre.org →

Why these techniques?

Vulnerability triggered by opening crafted AVI file enables user execution of malicious file (T1204.002) and application crash via exploitation (T1499.004).

Confidence: MEDIUM · MITRE ATT&CK Enterprise v18.1

NVD Description

A flaw was found in libtheora. This heap-based out-of-bounds read vulnerability exists within the AVI (Audio Video Interleave) parser, specifically in the avi_parse_input_file() function. A local attacker could exploit this by tricking a user into opening a specially crafted AVI…

file containing a truncated header sub-chunk. This could lead to a denial-of-service (application crash) or potentially leak sensitive information from the heap.

Deeper analysisAI

CVE-2026-5673 is a heap-based out-of-bounds read vulnerability (CWE-125) in the libtheora library, specifically within the AVI parser's avi_parse_input_file() function. The issue arises when processing a specially crafted AVI file with a truncated header sub-chunk, affecting applications that use libtheora for Theora video decoding.

A local attacker with low privileges can exploit this vulnerability by tricking a user into opening a malicious AVI file. This requires low attack complexity and user interaction but no elevated privileges or scope changes. Exploitation leads to a denial-of-service (application crash, high availability impact) or potential leakage of sensitive heap information (low confidentiality impact), as scored at CVSS 5.6 (CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:H).

Advisories and patches for mitigation are detailed in the Red Hat security bulletin at https://access.redhat.com/security/cve/CVE-2026-5673, the associated Bugzilla entry at https://bugzilla.redhat.com/show_bug.cgi?id=2455340, and the upstream GitHub issue at https://github.com/xiph/theora/issues/24.