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CVE Record

CVE-2020-17525: Remote unauthenticated denial-of-service in Subversion mod_authz_svn

Subversion's mod_authz_svn module will crash if the server is using in-repository authz rules with the AuthzSVNReposRelativeAccessFile option and a client sends a request for a non-existing repository URL. This can lead to disruption for users of the service. This issue was fixed in mod_dav_svn+mod_authz_svn servers 1.14.1 and mod_dav_svn+mod_authz_svn servers 1.10.7

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2020-17525 can let an unauthenticated remote client crash certain Apache Subversion web servers. The business impact is service disruption for users who depend on Subversion repositories. Exposure depends on a specific authorization configuration, so not every Subversion deployment is affected.

Executive priority

Treat this as a focused availability risk. Prioritize internet-facing or business-critical Subversion services, especially where repository access supports engineering delivery. It is lower urgency than a data compromise flaw, but outages can disrupt builds, releases, and developer workflows.

Technical view

The flaw is a NULL pointer dereference in Subversion's mod_authz_svn when used with mod_dav_svn, in-repository authz rules, and AuthzSVNReposRelativeAccessFile. A request for a non-existing repository URL can crash the server component. The issue is fixed in Subversion 1.14.1 and 1.10.7 server packages.

Likely exposure

Likely exposed systems are Apache Subversion HTTP(S) servers using mod_dav_svn plus mod_authz_svn with in-repository authorization rules and AuthzSVNReposRelativeAccessFile. Deployments not using that configuration, or updated to fixed versions, appear less likely to be affected based on the provided sources.

Exploitation context

The sources describe remote unauthenticated denial of service, not code execution or data theft. KEV is false, and the provided bundle contains no evidence of active exploitation. The described trigger involves a non-existing repository URL, but no weaponization details are provided here.

Researcher notes

CWE-476 maps to NULL pointer dereference. The affected condition is configuration-specific, so validation should prove mod_dav_svn, mod_authz_svn, in-repository authz, and AuthzSVNReposRelativeAccessFile are present. The bundle does not provide CVSS, exploit telemetry, or detailed workaround language beyond fixed versions.

Mitigation direction

  • Upgrade affected Subversion servers to 1.14.1, 1.10.7, or a later vendor-fixed release.
  • Apply Debian or operating system security updates where Subversion is installed from distribution packages.
  • Review whether AuthzSVNReposRelativeAccessFile and in-repository authz rules are required.
  • Check Apache Subversion security guidance for any deployment-specific workarounds or hardening notes.

Validation and detection

  • Inventory Subversion servers exposed over HTTP(S) using mod_dav_svn and mod_authz_svn.
  • Confirm installed Subversion server package versions against 1.14.1, 1.10.7, or later fixed builds.
  • Review server configuration for AuthzSVNReposRelativeAccessFile and in-repository authz usage.
  • Check service logs for unexplained crashes or restarts around invalid repository URL requests.
Prepared
Confidence
high
Sources
4

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

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ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-476: Exact CWE lookup

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cve · low confidence lookup

CVE-2020-17525 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
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.

0CVSS vectors
0Timeline events
0ADP providers
3Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Apache Software FoundationApache Subversionmod_authz_svn 1.10.7, mod_authz_svnListed
Weakness

CWE details

CWE-476

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

CWE-476 · source CWE mapping

NULL Pointer Dereference

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

Open CWE intelligenceSame-CWE CVEs