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Response snapshot Oct 26, 2026, 23:53 UTC

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VulnerabilityCVE-2026-61642

Squid is a caching proxy for the Web.

Squid is a caching proxy for the Web. From 3.3.0.1 to before 7.6, due to an improper enforcement of behavioral workflow bug, Squid is vulnerable to a Request Smuggling attack against HTTP/1.1 Transfer-Encoding. HTTP header parsing (`src/HttpHeader.

At a glance

Exploited
Not known
Severity
7.7 High (CVSS 3.1)
Chance of exploitation
2.2% in the next 30 days
Sources
1 source

What to do

Check the vendor advisory for affected versions and fixes.

Read NVD CVE-2026-61642 (opens a new tab)

What happened

Squid is a caching proxy for the Web. From 3.3.0.1 to before 7.6, due to an improper enforcement of behavioral workflow bug, Squid is vulnerable to a Request Smuggling attack against HTTP/1.1 Transfer-Encoding. HTTP header parsing (`src/HttpHeader.cc`) accepted the bare` Transfer-Encoding:` identity form, which the HTTP specification prohibits because any transfer coding must be wrapped within chunked encoding.

This problem allows a trusted client to perform an HTTP Request Smuggling attack when HTTP/1.1 is used, bypassing security mechanisms that may be in place between attacker and Squid.

When there is an HTTP cache operating prior to the affected Squid, this Request Smuggling attack also allows the attacker to poison that web cache and store arbitrary malicious content at any URL for delivery to other clients' future requests. This issue is fixed in version 7.6.

Scores and how they were measured

CVSS base severity

7.7

Version 3.1As of

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

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

2.2%

Scored Percentile 82.6%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Sources

  1. Primary source

    NVD CVE-2026-61642 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  2. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  3. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-61642, scored 2026-10-26. A model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 16). Squid is a caching proxy for the Web. (CVE-2026-61642). https://kevwire.com/record/CVE-2026-61642

MLA

"Squid is a caching proxy for the Web. (CVE-2026-61642)." KEVWire, 16 Oct. 2026, kevwire.com/record/CVE-2026-61642.

Chicago

KEVWire. "Squid is a caching proxy for the Web. (CVE-2026-61642)." Last modified October 16, 2026. https://kevwire.com/record/CVE-2026-61642.

Evidence summary (plain text)

Squid is a caching proxy for the Web. (Oct 13, 2026).
Squid is a caching proxy for the Web. From 3.3.0.1 to before 7.6, due to an improper enforcement of behavioral workflow bug, Squid is vulnerable to a Request Smuggling attack against HTTP/1.1 Transfer-Encoding. HTTP header parsing (`src/HttpHeader.cc`) accepted the bare` Transfer-Encoding:` identity form, which the HTTP specification prohibits because any transfer coding must be wrapped within chunked encoding. This problem allows a trusted client to perform an HTTP Request Smuggling attack when HTTP/1.1 is used, bypassing security mechanisms that may be in place between attacker and Squid. When there is an HTTP cache operating prior to the affected Squid, this Request Smuggling attack also allows the attacker to poison that web cache and store arbitrary malicious content at any URL for delivery to other clients' future requests. This issue is fixed in version 7.6.
CVSS 7.7 (version 3.1; evidence as of Oct 16, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-61642).
EPSS 2.2% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-61642&date=2026-10-26).
Sources:
NVD CVE-2026-61642: https://nvd.nist.gov/vuln/detail/CVE-2026-61642
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-61642
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-61642&date=2026-10-26
Record ID: CVE-2026-61642.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 26, 2026, 23:54 UTC. Ingestion is not an independent editorial investigation.

NVD status: Awaiting Analysis. Publication in the NVD is not evidence of exploitation.

Looked up on demand from NVD because this CVE is outside the regularly tracked set (older, or rated below HIGH). It is not in CISA's Known Exploited Vulnerabilities catalog as of the last ingestion.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

Record JSON

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Record details

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