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Fencer Intel
high 7.5

CVE-2021-41611 json

An issue was discovered in Squid 5.0.6 through 5.1.x before 5.2.

published 5y ago modified 4mo ago also EUVD-2021-28625

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.9%
EPSS 2.9% chance of exploitation in 30 days, percentile 87%
public exploits
0
none known

Summary

An issue was discovered in Squid 5.0.6 through 5.1.x before 5.2. When validating an origin server or peer certificate, Squid may incorrectly classify certain certificates as trusted. This problem allows a remote server to obtain security trust well improperly. This indication of trust may be passed along to clients, allowing access to unsafe or hijacked services.

Patch / fix

  • squid-cache squid 5.2
  • squid Debian 14, Debian 13, Debian 12 5.2-1

debian advisories DEBIAN-CVE-2021-41611

  • squid Alpine 3.14, Alpine 3.13 5.0.6-r2
  • squid Alpine 3.24, Alpine 3.23, Alpine 3.22 +7 more 5.2-r0

alpine advisories ALPINE-CVE-2021-41611

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • squid Arch Linux 5.2-1

arch linux advisories AVG-1667

Is CVE-2021-41611 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-41611 updated cvss 8.1

squid: improper certificate validation

  • Red Hat Enterprise Linux 6 squid Red Hat Enterprise Linux 7 squid, squid-sysvinit, squid-migration-script Red Hat Enterprise Linux 8 squid, libecap Red Hat Enterprise Linux 9 squid
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

2.95% chance of exploitation in the next 30 days, higher than 87% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:P/I:N/A:N

Classification

Weakness
  • CWE-295 Improper Certificate Validation

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.