CESNET ipfixcol2 2.7.1 before 2.9.0 contains a memory allocation vulnerability in Lz4Decoder::read_start_header() that
Source GCVE Database
Not known to be exploited · CVSS 6.9 Medium : upgrade to 2.9.0 when convenient.
Data as of 4 Nov 2026, 22:39 UTC
Thin evidence
One scorer or none| CNA (VulnCheck) | CVSS 4.0 | 6.9 |
|---|---|---|
| CNA (VulnCheck) | CVSS 3.1 | 5.3 |
- Patch
- Available – fixed in 2.9.0
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:NExploitation evidence
Disclosed: evidence found.
CVE published 4 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 4 Nov 2026.
What to do
Upgrade ipfixcol2 and cesnet/ipfixcol2 to 2.9.0.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| CESNETipfixcol2 | Affected
| Fixed in
|
GitHubcesnet/ipfixcol2pkg:github/cesnet/ipfixcol2Other threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
If you cannot patch yet, consider limiting the rate of incoming TCP connections or applying network-level protections to mitigate potential denial of service attempts.
Description
CESNET ipfixcol2 versions 2.7.1 up to but not including 2.9.0 contain a memory allocation vulnerability in the Lz4Decoder::read_start_header() function. This flaw allows unauthenticated attackers to exhaust server memory by sending TCP connections with LZ4 start headers that declare very large ring buffer sizes, potentially forcing allocations up to 4 GiB per connection. The vulnerability can lead to denial of service by exhausting collector service resources.
References
- nvd.nist.gov/vuln/detail/CVE-2026-122129 (opens in a new tab)
- github.com/CESNET/ipfixcol2/commit/1a199033eff847941353c5c039cb806a9ad8aa6f (opens in a new tab)
- github.com/CESNET/ipfixcol2 (opens in a new tab)
- github.com/CESNET/ipfixcol2/blob/v2.8.0/src/plugins/input/tcp/src/Lz4Decoder.cpp (opens in a new tab)
- github.com/CESNET/ipfixcol2/releases/tag/v2.9.0 (opens in a new tab)
- vulncheck.com/advisories/cesnet-ipfixcol2-2.7.1-before-2.9.0-memory-exhaustion-via-tcp-lz4-decoder (opens in a new tab)