CVE-2026-43969: Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in ninenines cowlib allows HTTP req

Routine

LOW 3.2UPGRADE

CVE-2026-43969 is a low-severity flaw (CVSS 3.2) affecting cowlib. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in ninenines cowlib allows HTTP request splitting and cookie smuggling via unvalidated cookie name and value fields. cow_cookie:cookie/1 in cowlib builds a client-side Cookie: request header from a list of name-value pairs without validating either field. An attacker who controls the cookie names or values passed to this function can inject ;, ,, CR, LF, or TAB characters

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	3.2 (Low)
Attack vector	Local
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.1% (top 96%)
CISA exploited list	No
Weakness	CWE-93
Published	2026-05-11
Last modified	2026-10-26

Publisher (CNA): EEF · Vendor: ninenines

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-11 19:16 UTCPublished CVE record published
2026-10-26 20:10 UTCUpdated Record last modified

ninenines cowlib UPGRADE

Affected: >= 2.9.0 and <= 2.16.1

Fixed in: newer than 2.16.1

Safe to downgrade to: a release before 2.9.0

1. Check installed version

apt-cache policy cowlib || rpm -q cowlib || cowlib --version

2. UPGRADE to newer than 2.16.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade cowlib

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade cowlib

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 2.9.0 (Debian / Ubuntu)

apt-cache madison cowlib sudo apt install cowlib=<VERSION_BEFORE_2.9.0> sudo apt-mark hold cowlib

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list cowlib sudo dnf downgrade cowlib-<VERSION_BEFORE_2.9.0> sudo dnf versionlock add cowlib

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-43969?

cowlib: upgrade to newer than 2.16.1. Exact commands for each OS are on this page.

Is CVE-2026-43969 being exploited?

CVE-2026-43969 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-43969 affect?

CVE-2026-43969 affects cowlib. Severity is low (CVSS 3.2). Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in ninenines cowlib allows HTTP request splitting and cookie smuggling via unvalidated cookie name and value fields. cow_cookie:cookie/1 in cowlib builds a client-s

How urgent is CVE-2026-43969?

Priority 12/100. No elevated risk signals yet.

Related CVEs

CVE-2026-7790 HIGH 7.5 UPGRADE Uncontrolled Resource Consumption vulnerability in ninenines cowlib (cow_http_te module) allows Excessive Allo
CVE-2026-43968 MEDIUM 4.0 UPGRADE Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in ninenines cowlib allows SSE even

References

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