CVE-2026-43969

See a problem?
Please try reporting it to the source first.
Source
https://cve.org/CVERecord?id=CVE-2026-43969
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43969.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-43969
Aliases
Downstream
Published
2026-05-11T18:06:40.667Z
Modified
2026-08-20T03:30:14.777532120Z
Severity
  • 2.1 (Low) CVSS_V4 - CVSS: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 Calculator
Summary
Cookie Request Header Injection via Unvalidated Encoder in cow_cookie:cookie/1
Details

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.

cowcookie: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 into the serialized header. This enables two classes of attack: cookie smuggling within a single header (e.g. injecting ; admin=1 to introduce a phantom cookie that the receiving server treats as authentic) and HTTP request header splitting (injecting CRLF to append arbitrary headers or smuggle a complete second request against a shared upstream proxy). The decoder side (parsecookiename/1, parsecookie_value/1) and setcookie/3 already validate and reject these characters; the encoder alone is missing the check.

This issue affects cowlib: from 2.9.0 onward.

Database specific 
{
    "cwe_ids": [
        "CWE-93"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43969.json",
    "unresolved_ranges": [
        {
            "extracted_events": [
                {
                    "introduced": "2.9.0"
                },
                {
                    "fixed": "*"
                },
                {
                    "introduced": "f017f8a0ecbffd5033d9ab49bf180186f7a523a7"
                },
                {
                    "fixed": "*"
                }
            ],
            "source": "AFFECTED_FIELD"
        }
    ],
    "cna_assigner": "EEF"
}
References

Affected packages

Git / github.com/erlef/cowlib

Affected ranges

Type
GIT
Repo
https://github.com/erlef/cowlib
Events
Introduced
0 Unknown introduced commit / All previous commits are affected
Fixed
177953dd51540da11090666c1f007214127a1144
Database specific
Show details 
{
    "source": "REFERENCES"
}

Affected versions

0.*
0.1.0
0.2.0
0.3.0
0.4.0
0.5.0
0.5.1
0.6.0
0.6.1
0.6.2
1.*
1.0.0
1.0.1
1.1.0
1.2.0
1.3.0
2.*
2.0.0
2.0.0-pre.1
2.0.0-rc.1
2.0.1
2.1.0
2.10.0
2.10.1
2.11.0
2.12.0
2.12.1
2.13.0
2.14.0
2.15.0
2.16.0
2.2.0
2.2.1
2.3.0
2.4.0
2.5.0
2.5.1
2.6.0
2.7.0
2.7.1
2.7.2
2.7.3
2.8.0
2.9.0
2.9.1

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43969.json"

Git / github.com/ninenines/cowlib

Affected ranges

Type
GIT
Repo
https://github.com/ninenines/cowlib
Events
Introduced
b34155f725245848dca3a505398e262b1d50f25b
Last affected
bae6b022af54566f3518a3aa59083b4591d552de
Database specific
Show details 
{
    "extracted_events": [
        {
            "introduced": "2.9.0"
        },
        {
            "last_affected": "2.16.1"
        }
    ],
    "source": "CPE_RANGE",
    "cpe": "cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*"
}

Affected versions

2.*
2.10.0
2.10.1
2.11.0
2.12.0
2.12.1
2.13.0
2.14.0
2.15.0
2.16.0
2.16.1
2.9.0
2.9.1

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43969.json"