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VulnerabilityPublished

CVE-2026-43968: ninenines cowlib · CRLF Injection

Affects ninenines cowlibSource CVE Database V5

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Not known to be exploited · CVSS 6.3 Medium : upgrade to 2.16.1 when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 4.0 base score
6.3Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 18% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 2.16.1, 6165fc40efa159ba1cceee7e7981e790acba5d9c
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 11 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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 30 Oct 2026.

What to do

Upgrade cowlib to 2.16.1; cowlib to 6165fc40efa159ba1cceee7e7981e790acba5d9c.

Affected software

ProductAffectedFixed in
nineninescowlibAffected
  • >=2.6.0 <2.16.1
Fixed in
  • 2.16.1
nineninescowlibAffected
  • ≥ 93b2b897cde238506c803faad4d1602d79dba7c9, < 6165fc40efa159ba1cceee7e7981e790acba5d9c
Fixed in
  • 6165fc40efa159ba1cceee7e7981e790acba5d9c
Hexninenines/cowlibpkg:hex/ninenines/cowlibOther threatsAffected
  • =2.6.0
Fixed in–
Hexcowlibpkg:hex/cowlibOther threatsAffected
  • >=2.6.0 <2.16.1
Fixed in
  • 2.16.1

CPE configurations (1)

  • cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*

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 implementing input validation or sanitization on fields used in SSE events to block carriage return characters or other control characters that could enable injection.

Description

CVE-2026-43968 is a CRLF injection vulnerability in ninenines cowlib versions from 2.6.0 before 2.16.1. It arises because the library improperly neutralizes carriage return (\r) characters in Server-Sent Events (SSE) fields, allowing attackers to inject additional SSE lines. This can lead to event splitting and injection, enabling manipulation of client-side logic and potentially stored-XSS-like behavior when event data is rendered in browsers. The vulnerability has a CVSS 4.0 score of 6.3, indicating medium severity.

References

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