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Apache EUVDEUVD-2026-64000

| CVE-2026-54789 HIGH
Out-of-bounds Read (CWE-125)
2026-08-21 security-advisories@github.com
Buffer Overflow Apache Information Disclosure
7.5
CVSS 3.1 · Vendor: github
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Vulnerability Assessment

Weakness
CWE
CWE-125
ASVS 5.0
V15 - Secure Coding and Architecture Bounds checking, read limits
MITRE ATT&CK

1 technique across 1 tactic: Collection

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

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This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 0.4% exploitation probability (EPSS)

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AnalysisAIv1 – Aug 21, 2026

Out-of-bounds read and one-byte out-of-bounds write in mod_auth_openidc's state-cookie parser (all versions prior to 2.4.19.4) allow unauthenticated remote attackers to crash Apache worker processes by sending a malformed Cookie header. The root cause is a loop termination condition in src/state.c that checked whether a pointer was NULL — a condition that could never fire since the pointer is only ever incremented — rather than checking for the string terminator, causing state-prefixed cookie tokens lacking '=' to scan and write past the end of the token buffer. No CISA KEV listing or confirmed public exploit exists at time of analysis, but the CVSS AV:N/AC:L/PR:N profile and the fully transparent fix commit make this trivially automatable for denial-of-service once widely known.

Affected VersionsENISA

mod_auth_openidc < 2.4.19.4

Affected Packages

euvd mod_auth_openidc fix: 2.4.19.4

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

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  • Exploit and PoC references, threat intelligence from 22 sources
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Severity by source

Vendor (github) PRIMARY 7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SUSE HIGH
Red Hat 7.5 HIGH

Primary rating from Vendor (github).

CVSS VectorVendor: github

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Lifecycle Timeline

2
Patch available
Aug 21, 2026 - 17:16 EUVD
CVE Published
Aug 21, 2026 - 16:17 cve.org
HIGH 7.5

DescriptionCVE.org

mod_auth_openidc is an OpenID Certified authentication and authorization module for the Apache 2.x HTTP server that implements the OpenID Connect Relying Party functionality. Prior to 2.4.19.4, an out-of-bounds read and a one-byte out-of-bounds write exist in the state-cookie parser of mod_auth_openidc. The issue is fixed in version 2.4.19.4 by stopping the scan at the string terminator so a value-less token is rejected. No in-product workarounds are available. As a stop-gap, an upstream reverse proxy or WAF that rejects or normalizes malformed Cookie headers (tokens lacking =) can reduce exposure, but upgrading is the recommended remediation.

Articles & Coverage 1

News 9 New Apache Vulnerabilities - 1 Critical, 8 High Severity Aug 22, 2026

Executive ViewAI

Why It Matters

mod_auth_openidc versions prior to 2.4.19.4 contain an unauthenticated remote denial-of-service vulnerability allowing attackers to crash Apache worker processes via malformed HTTP requests, directly disrupting authentication service availability. All organizations running affected versions face immediate operational risk without compensating controls.

Recommended Action

Within 24 hours, complete an inventory of all Apache instances running mod_auth_openidc and identify systems with versions prior to 2.4.19.4, prioritizing authentication-critical infrastructure. Within 7 days, deploy interim mitigations including WAF rules to reject malformed Cookie headers, enable Apache process auto-restart with connection limits to contain crash impact, and implement detailed error logging for exploitation detection. Within 30 days, obtain and test the vendor patch when released and execute phased production upgrades, or finalize comprehensive compensating control deployment if patching is delayed.

Business Impact: High
Compensating Controls

No vendor-released patch identified at time of analysis. Interim mitigations: Web Application Firewall rules to block malformed Cookie headers; Apache MaxConnectionsPerChild tuning to recycle worker processes and limit crash blast radius; process-level monitoring with automatic restart capability; reverse proxy cookie validation upstream; comprehensive access and error logging to detect exploitation attempts.

Threat Intelligence Overview

EPSS Score
0.4%
Top 67% exploitable
Data Quality
8 sources
Confidence: High
EUVD NVD CVE.org EPSS Vulnrichment Vendor GitHub VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC No
EPSS 0.4%
Patch available Yes
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
Yes
Human Impact
High
Technical Impact
Partial

Priority Score

38
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +38
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Buffer Overflow HIGH

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
SUSE Linux Enterprise Server 12 SP5-LTSS Fixed
SUSE Linux Enterprise Server LTSS Extended Security 12 SP5 Fixed
openSUSE Leap 16.0 Fixed
openSUSE Tumbleweed Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS Affected

References

Advisories & patches
ADVISORY https://vuldb.com/vuln/394140 REF https://github.com/OpenIDC/mod_auth_openidc/commit/8017478471cc071c49aa073c5c9be652a73a8630 REF https://github.com/OpenIDC/mod_auth_openidc/security/advisories/GHSA-vgr5-qcpp-x2pr REF https://lists.debian.org/debian-lts-announce/2026/09/msg00003.html

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