Out-of-bounds Read in Xiph Theora
CVE-2026-5673
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.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.6 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:H.
EPSS exploit prediction
EPSS: 0.002 (4.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 5th percentile — 4.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: -0.000
Affected products
Weakness classification (CWE)
References
- access.redhat.com/security/cve/CVE-2026-5673 (Third Party Advisory, vdb-entry)
- bugzilla.redhat.com/show_bug.cgi (issue-tracking, Third Party Advisory, Issue Tracking)
- github.com/xiph/theora/issues/24 (Exploit, Third Party Advisory, Issue Tracking)
Frequently asked questions
- What is CVE-2026-5673?
- CVE-2026-5673 is a medium-severity vulnerability in Xiph Theora, classified under Out-of-bounds Read. CVSS score: 5.6/10. Published 2026-04-06.
- How severe is CVE-2026-5673?
- Medium severity. CVSS v3 base score is 5.6 out of 10.