Is CVE-2026-9658 in the CISA KEV catalog?

No. CVE-2026-9658 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-9658?

CVE-2026-9658 has a CVSS v3 base score of 7.3 (HIGH).

What is the EPSS score for CVE-2026-9658?

CVE-2026-9658 has an EPSS score of 0.23% (13th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix or mitigate CVE-2026-9658?

No published fix for CVE-2026-9658 has been found yet. Check the linked vendor advisories for guidance as it becomes available.

CVE & CISA-KEV Catalog

CVE-2026-9658

HIGH

7.3

CVSS v3

NVD

Description

Plack::Middleware::Security::Common versions before 0.13.1 for Perl did not block header injections in request paths. The header injection rule was ineffective at blocking header injections in the request paths unless they were double-encoded, for example, GET /path\r\nHTTP/1.1\r\nHost: secret.example.com Note that it is unclear whether request paths with CRLF followed by additional headers would be blocked by reverse proxies, or how they would be processed by Plack-based servers.

CWE-113 CWE-790

How to fix

No published remediation has been found for this vulnerability's affected products yet.

Mitigation guidance may be in the linked vendor advisories in the References section below.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityLow

IntegrityLow

AvailabilityLow

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

Exploit Intelligence

0.23%probability of exploitation in 30 days

13thpercentile

Low risk: more likely to be exploited than 13% of all known CVEs.

References

Other references2

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-06-01.