CESNET ipfixcol2 2.7.1 before 2.9.0 Memory Exhaustion via TCP LZ4 Decoder
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 2.9.0
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 2.9.0.
- Exploitation?/40Exploitation: unknown (data gap). No CISA SSVC exploitation rating yet
- Exposure17/25No login or user action needed per the CVSS vector, reachable over the network without a login · Data gap: No advisory context yet
- Reach?/20Reach: unknown (data gap). No tracked technology or package matched
- Severity6.9/10CVSS 6.9
- No patch0/5No signal
What would change the score
- Would score about 69 if added to CISA KEV
- Would score about 64 if CISA's SSVC rates exploitation active
- Would score about 29 if advisories confirm default setups are exposed
CVE-2026-122129 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 6.9 (medium) and affects ipfixcol2; fixed in 2.9.0.
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- Published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 24/100 · provisional
- Fix
- Fixed in 2.9.0
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
CESNET ipfixcol2 versions before 2.9.0 (ipfixcol2 2.7.1 and later affected range) can be made to exhaust memory through its TCP LZ4 decoder. An attacker can reach it remotely, without logging in, by opening TCP connections with LZ4 start headers that declare very large buffer sizes, forcing huge allocations and denying the collector service.
Read the original description
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.
What to do
Upgrade to a fixed version: 2.9.0.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- CESNET ipfixcol2
From 2.7.1 · fixed in 2.9.0
Evidence 5
- Patch
- Repository
- Repository
- Repository
- Link
Corrections
None so far.
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Questions about CVE-2026-122129
Is CVE-2026-122129 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
Which versions are affected by CVE-2026-122129?
ipfixcol2: from 2.7.1 before 2.9.0.Source: cve.now feed data
How do I fix CVE-2026-122129?
Upgrade to a fixed version: 2.9.0.Source: cve.now feed data