Is CVE-2026-54387 in the CISA KEV catalog?

No. CVE-2026-54387 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-54387?

CVE-2026-54387 has a CVSS v3 base score of 9.1 (CRITICAL).

What is the EPSS score for CVE-2026-54387?

CVE-2026-54387 has an EPSS score of 0.39% (30th percentile), estimating the probability of exploitation in the next 30 days.

CVE & CISA-KEV Catalog

CVE-2026-54387

CRITICAL

9.1

CVSS v3

NVD

Description

Tinyproxy through 1.11.3, fixed in commit ff45d3b, fails to reconcile conflicting Content-Length and Transfer-Encoding: chunked headers, forwarding both verbatim to the backend while using Content-Length to determine how many request body bytes to consume. Remote attackers can desynchronize the proxy and backend parser state, allowing injection of arbitrary HTTP requests to the backend to enable cache poisoning, access control bypass, and request hijacking.

CWE-444

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityNone

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

Exploit Intelligence

0.39%probability of exploitation in 30 days

30thpercentile

Low risk: more likely to be exploited than 30% of all known CVEs.

References

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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 2026-06-22.