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CVE-2023-39953

18
FAUCET Score

CVE-2023-39953 is a medium-severity vulnerability affecting the user_oidc app for Nextcloud, versions 1.0.0 through 1.3.2. The flaw, a missing issuer verification (CWE-303), could allow a man-in-the-middle attacker to inject corrupted or known tokens. With a CVSS score of 4.8, this vulnerability has a network attack vector and high attack complexity, potentially leading to limited confidentiality and integrity impacts. There is no evidence of active exploitation, public exploit code, or significant community discussion, and it is not listed in CISA's KEV catalog.

Impacted Technologies

VendorProductVersion(s)CPE
>= 1.0.0, < 1.3.3CPE matchmatch criteria
cpe:2.3:a:nextcloud:user_oidc:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

4.8MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
2.2
Impact Score
2.5
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.45%
Probability of exploitation in next 30 days
EPSS Percentile
36.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0045 is in the 5th percentile among its peer group of 19,958 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.0 Bluesky, 0.0 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

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

Remediation

Patch Available

Vendor Patches (1)

github_advisorypatch availablevia nvd_reference
View patch

References

github.com / nextcloud/security-advisories/security/advisories/GHSA-xx3h-v363-q36j
PatchVendor Advisory
github.com / nextcloud/user_oidc/pull/642
Patch
hackerone.com / reports/2021684
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