# CVE-2025-3891: Mod_auth_openidc: dos via empty post in mod_auth_openidc with oidcpreservepost enabled Status: published. Published: 2025-04-29. Updated: 2026-11-04. 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. ## Remediation No remediation reported in collected sources ## Affected products and versions - / (mod_auth_openidc): ≥ 2.0.0; < 2.4.13.1 (affected, semver). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 8 (mod_auth_openidc:2.3): ≥ 8100020250426100353.489197e6; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 8.2 Advanced Update Support (mod_auth_openidc:2.3): ≥ 8020020250612174445.4cda2c84; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support (mod_auth_openidc:2.3): ≥ 8040020250618101351.522a0ee4; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support (mod_auth_openidc:2.3): ≥ 8060020250617090503.ad008a3a; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 8.6 Telecommunications Update Service (mod_auth_openidc:2.3): ≥ 8060020250617090503.ad008a3a; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions (mod_auth_openidc:2.3): ≥ 8060020250617090503.ad008a3a; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 8.8 Telecommunications Update Service (mod_auth_openidc:2.3): ≥ 8080020250617090716.63b34585; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions (mod_auth_openidc:2.3): ≥ 8080020250617090716.63b34585; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 9 (mod_auth_openidc): ≥ 0:2.4.10-1.el9_6.2; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions (mod_auth_openidc): ≥ 0:2.4.9.4-1.el9_0.3; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions (mod_auth_openidc): ≥ 0:2.4.9.4-1.el9_2.3; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 9.4 Extended Update Support (mod_auth_openidc): ≥ 0:2.4.9.4-4.el9_4.2; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 10 (mod_auth_openidc): Version range not reported. Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 7 (mod_auth_openidc): Version range not reported. Source: CNA: redhat ## NVD configuration conditions Affected CPE matches depend on the following AND/OR and negation conditions: ```json [ { "negate": false, "nodes": [ { "cpeMatch": [ { "criteria": "cpe:2.3:a:apache:http_server:-:*:*:*:*:*:*:*", "vulnerable": true } ], "negate": false, "operator": "OR" } ], "operator": "OR" }, { "negate": false, "nodes": [ { "cpeMatch": [ { "criteria": "cpe:2.3:o:redhat:enterprise_linux:7.0:*:*:*:*:*:*:*", "vulnerable": true }, { "criteria": "cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:-:*:*:*", "vulnerable": true }, { "criteria": "cpe:2.3:o:redhat:enterprise_linux:9.0:*:*:*:*:*:*:*", "vulnerable": true } ], "negate": false, "operator": "OR" } ], "operator": "OR" }, { "negate": false, "nodes": [ { "cpeMatch": [ { "criteria": "cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*", "vulnerable": true } ], "negate": false, "operator": "OR" } ], "operator": "OR" } ] ``` ## Severity and prioritization - CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: redhat - CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: NVD: secalert@redhat.com - CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: NVD: nvd@nist.gov - CISA KEV: No listing in collected sources - EPSS: 1.60% as of 2026-11-04; percentile 75.92% - SSVC: exploitation none; automatable yes; technical impact partial; source ADP: CISA-ADP - Weaknesses: CWE-248 ## Exploit evidence No exploit evidence in collected sources. This is not proof of no exploitation. ## References - https://access.redhat.com/errata/RHSA-2025:10002 (CNA: redhat; vendor-advisory, x_refsource_REDHAT) - https://access.redhat.com/errata/RHSA-2025:10003 (CNA: redhat; vendor-advisory, x_refsource_REDHAT) - https://access.redhat.com/errata/RHSA-2025:10004 (CNA: redhat; vendor-advisory, x_refsource_REDHAT) - https://access.redhat.com/errata/RHSA-2025:10006 (CNA: redhat; vendor-advisory, x_refsource_REDHAT) - https://access.redhat.com/errata/RHSA-2025:10007 (CNA: redhat; vendor-advisory, x_refsource_REDHAT) - https://access.redhat.com/errata/RHSA-2025:10008 (CNA: redhat; vendor-advisory, x_refsource_REDHAT) - https://access.redhat.com/errata/RHSA-2025:10010 (CNA: redhat; vendor-advisory, x_refsource_REDHAT) - https://access.redhat.com/errata/RHSA-2025:4597 (CNA: redhat; vendor-advisory, x_refsource_REDHAT) - https://access.redhat.com/errata/RHSA-2025:9396 (CNA: redhat; vendor-advisory, x_refsource_REDHAT) - https://access.redhat.com/security/cve/CVE-2025-3891 (CNA: redhat; vdb-entry, x_refsource_REDHAT) - https://bugzilla.redhat.com/show_bug.cgi?id=2361633 (CNA: redhat; issue-tracking, x_refsource_REDHAT) - https://github.com/OpenIDC/mod_auth_openidc/commit/6a0b5f66c87184dfe0e4400f6bdd46a82dc0ec2b (CNA: redhat) - https://github.com/OpenIDC/mod_auth_openidc/security/advisories/GHSA-x7cf-8wgv-5j86 (CNA: redhat) - https://lists.debian.org/debian-lts-announce/2025/05/msg00007.html (ADP: CVE) - https://access.redhat.com/errata/RHSA-2025:10002 (secalert@redhat.com) - https://access.redhat.com/errata/RHSA-2025:10003 (secalert@redhat.com) - https://access.redhat.com/errata/RHSA-2025:10004 (secalert@redhat.com) - https://access.redhat.com/errata/RHSA-2025:10006 (secalert@redhat.com) - https://access.redhat.com/errata/RHSA-2025:10007 (secalert@redhat.com) - https://access.redhat.com/errata/RHSA-2025:10008 (secalert@redhat.com) - https://access.redhat.com/errata/RHSA-2025:10010 (secalert@redhat.com) - https://access.redhat.com/errata/RHSA-2025:4597 (secalert@redhat.com; Third Party Advisory) - https://access.redhat.com/errata/RHSA-2025:9396 (secalert@redhat.com) - https://access.redhat.com/security/cve/CVE-2025-3891 (secalert@redhat.com; Third Party Advisory) - https://bugzilla.redhat.com/show_bug.cgi?id=2361633 (secalert@redhat.com; Issue Tracking) - https://github.com/OpenIDC/mod_auth_openidc/commit/6a0b5f66c87184dfe0e4400f6bdd46a82dc0ec2b (secalert@redhat.com) - https://github.com/OpenIDC/mod_auth_openidc/security/advisories/GHSA-x7cf-8wgv-5j86 (secalert@redhat.com) - https://lists.debian.org/debian-lts-announce/2025/05/msg00007.html (af854a3a-2127-422b-91ae-364da2661108; Mailing List, Third Party Advisory) ## Provenance - CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2025-3891; retrieved 2026-11-04; source updated 2026-11-04 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-3891; retrieved 2026-11-05; source updated 2026-11-04 - FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2025-3891; retrieved 2026-11-04; source updated Not reported Revision: 4e220b2533838ff41934d7bd914d28093b7b5b9273a811f400a202f0a8b85f51 Canonical: https://y2.dev/cve/CVE-2025-3891 ## Agent and API access Public CVE pages, Markdown, and JSON are free to read without an account or API key. - Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end. - WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers. - Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}. - Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer . Setup: https://y2.dev/docs/api/create-key. - x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402. - OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json. Collected public records only. Check source status for coverage and freshness.