HTTP ServerWeb server / proxy · Apache
CVE-2020-35452
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedApache HTTP Server versions 2.4.0 to 2.4.46 A specially crafted Digest nonce can cause a stack overflow in mod_auth_digest. There is no report of this overflow being exploitable, nor the Apache HTTP Server team could create one, though some particular compiler and/or compilation option might make it possible, with limited consequences anyway due to the size (a single byte) and the value (zero byte) of the overflow
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceA stack-based buffer overflow vulnerability exists in mod_auth_digest of Apache HTTP Server versions 2.4.0 through 2.4.46. The flaw is triggered when processing a specially crafted Digest nonce, causing a one-byte overflow with a zero value. While the overflow has limited exploitability due to its size and value, the CVSS score of 7.3 reflects the potential for authenticated attackers to cause denial of service or potentially execute code under specific compiler conditions.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
HTTP ServerWeb server / proxy
>= 2.4.0, <= 2.4.46
Debian LinuxOperating system
= 9.0= 10.0
FedoraOperating system
= 34= 35= 12.4.0.0= 17.1= 17.2= 17.3= 8.8CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- Low
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify Apache HTTP Server installation and versionRun 'httpd -v' or 'apache2 -v' to get the installed Apache version numberAffected if The version displayed is 2.4.0 through 2.4.46 inclusive
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Verify mod_auth_digest module is loadedRun 'httpd -M' or 'apache2ctl -M' and look for 'auth_digest_module' in the loaded modules list, or check for 'LoadModule auth_digest_module' in the httpd.conf/apache2.conf configuration filesAffected if The auth_digest_module appears in the loaded modules list
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Check if Digest authentication is configuredSearch configuration files (httpd.conf, apache2.conf, .htaccess files) for 'AuthType Digest' or 'AuthDigest*' directives, or check for 'mod_auth_digest' being used in any VirtualHost or directory blocksAffected if Digest authentication is explicitly configured and enabled in any Apache configuration context
You are affected if Apache HTTP Server version 2.4.0-2.4.46 is installed AND the mod_auth_digest module is loaded AND Digest authentication is actively configured in use.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataUpgrade Apache HTTP Server to version 2.4.47 or later to obtain the patched version of mod_auth_digest. If immediate patching is not feasible, consider restricting network access to the affected Apache instance or disabling Digest authentication as a temporary workaround.
Fix this in HTTP Server
Scoped from the published advisory
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-35452 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-35452 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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