cve.bz

CVE-2026-61812

6.3 mediumEPSS 0.3%

Medium (6.3) in owasp-modsecurity modsecurity. EPSS 0.3% estimated probability of exploitation activity in the next 30 days.

On this page
ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. Prior to 2.9.15 and 3.0.17, t:htmlEntityDecode recognizes only a small subset of named HTML entities, so rules that depend on the transformation can inspect different bytes than a browser or backend. Attackers can encode ASCII separators and operators with unhandled entity names, including aliases, to bypass rules that depend on the transformation. The v3 decoder also accepts prefix matches instead of requiring an exact entity-token length, which can transform invalid longer names into different bytes. This issue is fixed in versions 2.9.15 and 3.0.17.

Severity

CVSS 4.0

6.3 medium
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N
EPSS
0.3% estimated probability of exploitation activity in the next 30 days; 25th percentile. Scored 2026-11-10. A forecast for this CVE across the internet, not for your own systems.
CWEs
CWE-172 Improper Encoding or Decoding of Data
CWE-180 Incorrect Behavior Order: Validate Before Canonicalize
Published
Assigned by
GitHub_M (CNA)
NVD analysis
Not in the NVD yet
Record from
the CVE List, synced

Ask an AI about this CVE

ChatGPTClaudeGoogle AI Mode

Show the promptExplain CVE-2026-61812 for an engineer deciding whether to act. Use https://cve.bz/api/public/cves/CVE-2026-61812?via=ask-ai-copy and https://cve.bz/cve/CVE-2026-61812?via=ask-ai-copy as the source of truth: what is affected and which versions fix it, whether it is in CISA KEV, public exploits, and its EPSS (an internet-wide 30-day estimate of exploitation activity, not a forecast for my systems). If they give no fixed versions, use the CVE record https://cveawg.mitre.org/api/cve/CVE-2026-61812 or the vendor advisory, not third-party mirrors. Tell me how to check whether I am affected and how to verify a fix. Cite the sources and say where they are uncertain.

Opens a third-party assistant; its answer is its own, not cve.bz's. The prompt holds only this CVE's id and public links.

Affected

Versions

From the CNA's record in the CVE List.

ProductAffected
owasp-modsecurity ModSecurity< 2.9.15
owasp-modsecurity ModSecurity>= 3.0.0, < 3.0.17

Linux distributions

DistributionReleasePackageFixed inAdvisory
Debian12, 13, 14modsecurity, modsecurity-apacheno fix listedDEBIAN-CVE-2026-61812
Ubuntu20.04:LTS, 22.04:LTS, 24.04:LTSmodsecurityno fix listedUBUNTU-CVE-2026-61812
Ubuntu26.04:LTS, 26.10modsecurity, modsecurity-apacheno fix listedUBUNTU-CVE-2026-61812
UbuntuPro:14.04:LTS, Pro:16.04:LTS, Pro:18.04:LTS and 3 moremodsecurity-apacheno fix listedUBUNTU-CVE-2026-61812
Azure Linux3mod_securityno fix listedAZL-113083

From the distributions' data via OSV.dev: the Debian Security Tracker; Ubuntu Security Notices © Canonical Ltd., CC BY-SA 4.0; Microsoft's Azure Linux vulnerability data, MIT. Modified: reformatted and linked to CVE records. Credits. On the distributions' own pages: Debian · Ubuntu.

Attack patterns (CAPEC)

  • CAPEC-3 Using Leading 'Ghost' Character Sequences to Bypass Input Filters Likelihood: Medium · Severity: Medium
  • CAPEC-71 Using Unicode Encoding to Bypass Validation Logic Likelihood: Medium · Severity: High
  • CAPEC-78 Using Escaped Slashes in Alternate Encoding Likelihood: High · Severity: High
  • CAPEC-79 Using Slashes in Alternate Encoding Likelihood: High · Severity: High
  • CAPEC-80 Using UTF-8 Encoding to Bypass Validation Logic Likelihood: High · Severity: High
  • CAPEC-267 Leverage Alternate Encoding Likelihood: High · Severity: High
  • CAPEC-52 Embedding NULL Bytes Likelihood: High · Severity: High
  • CAPEC-53 Postfix, Null Terminate, and Backslash Likelihood: High · Severity: High
  • CAPEC-64 Using Slashes and URL Encoding Combined to Bypass Validation Logic Likelihood: High · Severity: High
  • CAPEC-72 URL Encoding Likelihood: High · Severity: High

The attack patterns MITRE's CAPEC relates to this record's weaknesses, as MITRE names them. Credits. More on the page of CWE-172.

References

Check your stackJSON