CVE-2025-3891 | Mod_auth_openidc: dos via empty post in mod_auth_openidc with oidcpreservepost enabled

A flaw was found in the mod_auth_openidc module for Apache httpd. This flaw allows a remote, unauthenticated attacker to trigger a denial of service by sending an empty POST request when the OIDCPreservePost directive is enabled. The server crashes consistently, affecting availability.

Published: 2025-04-29 Last update: 2025-07-28 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-3891 is rated Moderate Risk (57.5/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.01%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2025-3891

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-07 0.67% 1.01% +0.34%
2 2026-05-25 1.33% 0.67% -0.66%
3 2026-02-23 — 1.33% —

Full EPSS history (29 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-3891

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2025-3891

OS Trackers for CVE-2025-3891

vendor priority summary link
debian not yet assigned CVE-2025-3891 not yet assigned priority: Debian including 1 source packages (libapache2-mod-auth-openidc), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2025-3891
redhat high — https://access.redhat.com/security/cve/CVE-2025-3891
suse high CVE-2025-3891 severity important: SUSE including 7 source package names (apache2-mod_auth_openidc-2.3.8-150100.3.34.1, apache2-mod_auth_openidc-2.4.0-7.22.1, …), 26 product×package rows across 24 product lines (SUSE Enterprise Storage 7.1, SUSE Liberty Linux 8, … (24 product lines)): Fixed 26. https://www.suse.com/security/cve/CVE-2025-3891/
ubuntu medium CVE-2025-3891 medium priority: Ubuntu including 1 source packages (libapache2-mod-auth-openidc), 9 status rows across 9 suites (bionic, focal, jammy, noble, oracular, plucky, questing, upstream, xenial): needs-triage 7, ignored 2. https://ubuntu.com/security/CVE-2025-3891

Affected software / configurations for CVE-2025-3891

Vendor Product Version Raw CPE
apache http_server — cpe:2.3:a:apache:http_server:-:*:*:*:*:*:*:*
redhat enterprise_linux 7.0 cpe:2.3:o:redhat:enterprise_linux:7.0:*:*:*:*:*:*:*
redhat enterprise_linux 8.0 cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:-:*:*:*
redhat enterprise_linux 9.0 cpe:2.3:o:redhat:enterprise_linux:9.0:*:*:*:*:*:*:*
debian debian_linux 11.0 cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*

References for CVE-2025-3891

URL Tags
https://access.redhat.com/errata/RHSA-2025:10002
https://access.redhat.com/errata/RHSA-2025:10003
https://access.redhat.com/errata/RHSA-2025:10004
https://access.redhat.com/errata/RHSA-2025:10006
https://access.redhat.com/errata/RHSA-2025:10007
https://access.redhat.com/errata/RHSA-2025:10008
https://access.redhat.com/errata/RHSA-2025:10010
https://access.redhat.com/errata/RHSA-2025:4597 Third Party Advisory
https://access.redhat.com/errata/RHSA-2025:9396
https://access.redhat.com/security/cve/CVE-2025-3891 Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2361633 Issue Tracking
https://github.com/OpenIDC/mod_auth_openidc/commit/6a0b5f66c87184dfe0e4400f6bdd46a82dc0ec2b
https://github.com/OpenIDC/mod_auth_openidc/security/advisories/GHSA-x7cf-8wgv-5j86
https://lists.debian.org/debian-lts-announce/2025/05/msg00007.html Mailing List Third Party Advisory
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