CVE-2026-122129— CESNET ipfixcol2 2.7.1 before 2.9.0 Memory Exhaustion via TCP LZ4 Decoder

Quick assessment

Affected

CESNET ipfixcol2

Exploitation

No confirmed in-the-wild exploitation; assess based on exposure

Recommended action

Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

CESNET ipfixcol2 2.7.1 至 2.9.0 之前的版本中，Lz4Decoder::read_start_header() 函数存在内存分配漏洞。该漏洞允许未认证的攻击者通过声明无界环形缓冲区大小来耗尽系统内存。攻击者可建立 TCP 连接，发送包含极大缓冲区大小的 LZ4 起始头，强制每个连接分配高达 4 GiB 的内存，从而导致采集器服务拒绝服务（DoS）。

CVSS 5.3 · Medium Updated Nov 05, 2026

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

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Vulnerability Information

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Vulnerability Title

CESNET ipfixcol2 2.7.1 before 2.9.0 Memory Exhaustion via TCP LZ4 Decoder

Source: CVE Program / CVE List V5

Vulnerability 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.

Source: CVE Program / CVE List V5

CVSS Information

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Source: CVE Program / CVE List V5

Vulnerability Type

未经控制的内存分配

Source: CVE Program / CVE List V5

Affected Products

Vendor	Product	Affected Versions	CPE	Subscribe
CESNET	ipfixcol2	2.7.1 ~ 2.9.0	-

II. Public POCs for CVE-2026-122129

#	POC Description	Source Link	Shenlong Link

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III. Intelligence Information for CVE-2026-122129

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Other References for CVE-2026-122129 (5)

https://github.com/CESNET/ipfixcol2 product
https://github.com/CESNET/ipfixcol2/blob/v2.8.0/src/plugins/input/tcp/src/Lz4Decoder.cpp#L126-L131 technical-description
https://github.com/CESNET/ipfixcol2/commit/1a199033eff847941353c5c039cb806a9ad8aa6f patch
https://github.com/CESNET/ipfixcol2/releases/tag/v2.9.0 release-notes
https://www.vulncheck.com/advisories/cesnet-ipfixcol2-2.7.1-before-2.9.0-memory-exhaustion-via-tcp-lz4-decoder third-party-advisory

https://www.cve.org/CVERecord?id=CVE-2026-122129

Same Patch Batch · CESNET · 2026-11-04 · 3 CVEs total

CVE-2026-122130	8.2 HIGH	CESNET ipfixcol2 2.3.0 before 2.9.0 Buffer Overflow via Forwarder Output Plugin
CVE-2026-122127	7.5 HIGH	CESNET ipfixcol2 2.7.1 before 2.9.0 Heap Buffer Overflow via TCP LZ4 Decoder

IV. Related Vulnerabilities

Same product: ipfixcol2

Same vendor: CESNET

Same weakness: CWE-789