Vulnerability in Cesnet Ipfixcol2
CVE-2026-122129
CESNET ipfixcol2 2.7.1 before 2.9.0 contains a memory allocation vulnerability in Lz4Decoder::read_start_header() that allows unauthenticated attackers to exhaust memory by declaring unbounded ring buffer sizes. Attackers can open TCP connections sending LZ4 start headers with very large buffer sizes, forcing up to 4 GiB allocations per connection and denying collector service.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/CESNET/ipfixcol2 (product)
- github.com/CESNET/ipfixcol2/blob/v2.8.0/src/plugins/input/tcp/src/Lz4Decoder.cpp (technical-description)
- Patch Commit (patch)
- ipfixcol2 v2.9.0 Release Notes (release-notes)
- VulnCheck Advisory: CESNET ipfixcol2 2.7.1 before 2.9.0 Memory Exhaustion via TCP LZ4 Decoder (third-party-advisory)
Frequently asked questions
- What is CVE-2026-122129?
- CVE-2026-122129 is a medium-severity vulnerability in Cesnet Ipfixcol2, classified under CWE-789. CVSS score: 5.3/10. Published 2026-11-04.
- How severe is CVE-2026-122129?
- Medium severity. CVSS v3 base score is 5.3 out of 10.