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CVE Record

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.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2025-3891 is an availability bug in Apache httpd deployments using mod_auth_openidc. When OIDCPreservePost is enabled, a remote unauthenticated request condition can consistently crash the server. The business risk is service outage, not data theft or privilege escalation based on the supplied sources.

Executive priority

Treat this as a high-priority availability issue for authentication infrastructure. It can disrupt access to protected applications without credentials. Patch exposed systems promptly and track exceptions because the sources describe consistent server crashes under the vulnerable configuration.

Technical view

The flaw is in mod_auth_openidc POST preservation handling when OIDCPreservePost is enabled. It is classified as CWE-248 with CVSS 3.1 score 7.5: network reachable, low complexity, no privileges, no user interaction, high availability impact, and no stated confidentiality or integrity impact.

Likely exposure

Exposure is most likely on Apache httpd servers using mod_auth_openidc with OIDCPreservePost enabled, especially listed Red Hat Enterprise Linux 8, 9, 10 streams and related EUS/AUS/E4S/TUS/SAP variants carrying affected packages.

Exploitation context

The source bundle says KEV is false and provides no cited evidence of active exploitation. However, the described condition is remote and unauthenticated with low attack complexity, so exposed identity front ends or login gateways should be prioritized for availability protection.

Researcher notes

Do not assume all mod_auth_openidc deployments are vulnerable; the supplied condition depends on OIDCPreservePost. The affected list is strongest for Red Hat package streams. The bundle includes an upstream commit and GitHub advisory, but no source here establishes active exploitation.

Mitigation direction

  • Identify Apache servers running mod_auth_openidc and check whether OIDCPreservePost is enabled.
  • Apply vendor-provided updates from Red Hat, Debian LTS, or OpenIDC guidance where applicable.
  • If patching is delayed, evaluate vendor-supported configuration changes for OIDCPreservePost risk reduction.
  • Prioritize internet-facing authentication gateways and high-availability customer portals first.
  • Monitor Apache crashes and restart loops until patched.

Validation and detection

  • Verify installed mod_auth_openidc package versions against the affected vendor package list.
  • Review Apache configuration for mod_auth_openidc usage and OIDCPreservePost enablement.
  • Confirm vendor advisories show the installed package is fixed or unaffected.
  • Check recent web server and system logs for repeated crashes or abnormal worker exits.
  • Document any exposed systems where patching or configuration mitigation is deferred.
Prepared
Confidence
high
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-248: Exact CWE lookup

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cve · low confidence lookup

CVE-2025-3891 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
5Timeline events
2ADP providers
15Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: partial

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6redhat

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2025-3891Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. Source timelineredhat

    Reported to Red Hat.

  2. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  3. Source timelineredhat

    Made public.

  4. CVE publishedCVE Program

    The CVE record was published.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Unknown vendormod_auth_openidcmod_auth_openidc, 2.0.0unaffected
Red HatRed Hat Enterprise Linux 8mod_auth_openidc:2.3, 8100020250426100353.489197e6affected
Red HatRed Hat Enterprise Linux 8.2 Advanced Update Supportmod_auth_openidc:2.3, 8020020250612174445.4cda2c84affected
Red HatRed Hat Enterprise Linux 8.4 Advanced Mission Critical Update Supportmod_auth_openidc:2.3, 8040020250618101351.522a0ee4affected
Red HatRed Hat Enterprise Linux 8.6 Advanced Mission Critical Update Supportmod_auth_openidc:2.3, 8060020250617090503.ad008a3aaffected
Red HatRed Hat Enterprise Linux 8.6 Telecommunications Update Servicemod_auth_openidc:2.3, 8060020250617090503.ad008a3aaffected
Red HatRed Hat Enterprise Linux 8.6 Update Services for SAP Solutionsmod_auth_openidc:2.3, 8060020250617090503.ad008a3aaffected
Red HatRed Hat Enterprise Linux 8.8 Telecommunications Update Servicemod_auth_openidc:2.3, 8080020250617090716.63b34585affected
Red HatRed Hat Enterprise Linux 8.8 Update Services for SAP Solutionsmod_auth_openidc:2.3, 8080020250617090716.63b34585affected
Red HatRed Hat Enterprise Linux 9mod_auth_openidc, 0:2.4.10-1.el9_6.2affected
Red HatRed Hat Enterprise Linux 9.0 Update Services for SAP Solutionsmod_auth_openidc, 0:2.4.9.4-1.el9_0.3affected
Red HatRed Hat Enterprise Linux 9.2 Update Services for SAP Solutionsmod_auth_openidc, 0:2.4.9.4-1.el9_2.3affected
Red HatRed Hat Enterprise Linux 9.4 Extended Update Supportmod_auth_openidc, 0:2.4.9.4-4.el9_4.2affected
Red HatRed Hat Enterprise Linux 10mod_auth_openidcaffected
Red HatRed Hat Enterprise Linux 7mod_auth_openidcunaffected
Weakness

CWE details

CWE-248

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-248 · source CWE mapping

Uncaught Exception

Uncaught Exception represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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