Buffer overflow in Cesnet Ipfixcol2
CVE-2026-122127
CESNET ipfixcol2 2.7.1 before 2.9.0 contains a heap-based buffer overflow in Lz4Decoder.cpp that allows unauthenticated network peers to write past heap buffers. Attackers can declare a small ring buffer_size followed by a large decompressed_size to write up to 65535 controlled bytes and crash the collector.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
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 Heap Buffer Overflow via TCP LZ4 Decoder (third-party-advisory)
Frequently asked questions
- What is CVE-2026-122127?
- CVE-2026-122127 is a high-severity vulnerability in Cesnet Ipfixcol2, classified under Out-of-bounds Write. CVSS score: 7.5/10. Published 2026-11-04.
- How severe is CVE-2026-122127?
- High severity. CVSS v3 base score is 7.5 out of 10.