How severe is CVE-2021-37843?

CVE-2021-37843 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-37843 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (74th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-37843?

CVE-2021-37843 primarily affects Atlassian Saml Single Sign On. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-37843?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-37843 published?

CVE-2021-37843 was published on 2021-08-02 and last updated on 2026-06-17.

CVE-2021-37843

CVE-2021-37843 is a critical-severity vulnerability in Atlassian Saml Single Sign On with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-306.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (74th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-306
Affected product: Atlassian Saml Single Sign On
Published: 2021-08-02
Last modified: 2026-06-17

Description

The resolution SAML SSO apps for Atlassian products allow a remote attacker to login to a user account when only the username is known (i.e., no other authentication is provided). The fixed versions are for Jira: 3.6.6.1, 4.0.12, 5.0.5; for Confluence 3.6.6, 4.0.12, 5.0.5; for Bitbucket 2.5.9, 3.6.6, 4.0.12, 5.0.5; for Bamboo 2.5.9, 3.6.6, 4.0.12, 5.0.5; and for Fisheye 2.5.9.

Frequently asked questions

What is CVE-2021-37843?: The resolution SAML SSO apps for Atlassian products allow a remote attacker to login to a user account when only the username is known (i.e., no other authentication is provided). The fixed versions are for Jira: 3.6.6.1, 4.0.12, 5.0.5; for Confluence 3.6.6, 4.0.12, 5.0.5; for Bitbucket 2.5.9, 3.6.6, 4.0.12, 5.0.5; for Bamboo 2.5.9, 3.6.6, 4.0.12, 5.0.5; and for Fisheye 2.5.9.
How severe is CVE-2021-37843?: CVE-2021-37843 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-37843 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (74th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-37843?: CVE-2021-37843 primarily affects Atlassian Saml Single Sign On. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-37843?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-37843 published?: CVE-2021-37843 was published on 2021-08-02 and last updated on 2026-06-17.

References

https://wiki.resolution.de/doc/saml-sso/5.0.x/all/security-advisories/2021-07-29-authentication-bypass-network-attacker-can-login-to-users-accounts-when-usernames-are-known

Affected products (5)

cpe:2.3:a:atlassian:saml_single_sign_on:*:*:*:*:*:bamboo:*:*
cpe:2.3:a:atlassian:saml_single_sign_on:*:*:*:*:*:bitbucket:*:*
cpe:2.3:a:atlassian:saml_single_sign_on:*:*:*:*:*:fisheye:*:*
cpe:2.3:a:atlassian:saml_single_sign_on:*:*:*:*:*:confluence:*:*
cpe:2.3:a:atlassian:saml_single_sign_on:*:*:*:*:*:jira:*:*

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