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CVE-2021-28091

24
FAUCET Score

CVE-2021-28091 is a high-severity cryptographic signature verification vulnerability affecting all versions of the Lasso library prior to 2.7.0, impacting various Debian and Fedora-based products. With a CVSS score of 7.5, this vulnerability allows an unauthenticated attacker to achieve high integrity impact over a network with low attack complexity. While there is no known active exploitation or public exploit code (Metasploit, Nuclei, ExploitDB), the vulnerability has garnered some community discussion and media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
< 2.7.0CPE matchmatch criteria
cpe:2.3:a:entrouvert:lasso:*:*:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
10.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
33CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
34CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
HIGH
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.32%
Probability of exploitation in next 30 days
EPSS Percentile
68.0%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0132 is in the 48th percentile among its peer group of 51,551 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (6)

microsoftpatch availablevia msrc
Product: 19479-16823Fixed in: 2.8.0-1
microsoftpatch availablevia msrc
Product: cbl2 lasso 2.8.0-1 on CBL Mariner 2.0Fixed in: 2.8.0-1
microsoftpatch availablevia msrc
Product: CBL Mariner 2.0 x64Fixed in: 2.8.0-1
microsoftpatch availablevia msrc
Product: CBL Mariner 2.0 ARMFixed in: 2.8.0-1
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: lasso-0:2.5.1-8.el7_9
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: lasso-0:2.6.0-12.el8
View patch

Vendor Advisories (3)

microsoft2022-Jan/CVE-2021-28091

CVE-2021-28091

Jan 11, 2022
microsoft2021-Jun/CVE-2021-28091Important

Lasso all versions prior to 2.7.0 has improper verification of a cryptographic signature.

Jun 8, 2021
redhatCVE-2021-28091Important

lasso: XML signature wrapping vulnerability when parsing SAML responses

Jun 1, 2021

References

listes.entrouvert.com / arc/lasso
Product
git.entrouvert.org / lasso.git/commit
PatchVendor Advisory
git.entrouvert.org / lasso.git/tree/NEWS
Release NotesVendor Advisory
lists.debian.org / debian-lts-announce/2021/06/msg00013.html
Mailing ListThird Party Advisory
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/SI4YAQF4VEV2KHQ6OXXZL7CJK7IZQ3EG
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/YSVWOHBBWLI2RB5C6TXINFEJRT4YSD3D
debian.org / security/2021/dsa-4926
Third Party Advisory