CVE-2026-43969

HTTP request splitting via unvalidated cookie fields

Published May 11, 2026 · Updated May 11, 2026

CRLF injection in Nine Nines Cowlib 2.9.0 and later allows attackers to split HTTP requests or smuggle cookies through crafted fields. cow_cookie:cookie/1 serializes caller-supplied cookie names and values into a Cookie request header without rejecting separators, CR, LF, or TAB. Exploitation requires an application to pass attacker-controlled bytes into this client-side encoder; successful injection can add headers, insert phantom cookies, or place a second request on a shared upstream connection.

CVSS severity2.1
Low
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

CRLF injection in Nine Nines Cowlib 2.9.0 and later allows attackers to split HTTP requests or smuggle cookies through crafted fields. cow_cookie:cookie/1 serializes caller-supplied cookie names and values into a Cookie request header without rejecting separators, CR, LF, or TAB. Exploitation requires an application to pass attacker-controlled bytes into this client-side encoder; successful injection can add headers, insert phantom cookies, or place a second request on a shared upstream connection.

The record

CVE
CVE-2026-43969
Published
May 11, 2026
Updated
May 11, 2026
Vendor
Nine Nines
Product
Cowlib
Classifications
CWE-93, CAPEC-105
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 11, 2026CVE publishedPublication date reported by the CVE source.
  2. May 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.9.0
  2. Affected versionversion=f017f8a0ecbffd5033d9ab49bf180186f7a523a7

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Nine Nines · Cowlibversion=2.9.0; version=f017f8a0ecbffd5033d9ab49bf180186f7a523a7

Published CVSS scores

2.1Erlang Ecosystem Foundation CNACVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-93Improper Neutralization of CRLF Sequences ('CRLF Injection')
CAPEC-105HTTP Request Splitting

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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