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CVE-2026-61619 OWASP CRS: ReDoS in shared unix-shell-evasion regex-assembly include (12 RCE rules) - PCRE2 backtracking-limit exhaustion causes detection bypass and CPU DoS

8.8 highEPSS 0.6%

High (8.8) in coreruleset coreruleset. EPSS 0.6% estimated probability of exploitation activity in the next 30 days.

On this page
The OWASP core rule set (CRS) is a set of generic attack detection rules for use with compatible web application firewalls. Prior to versions 3.3.10, 4.25.1, and 4.28.0, regular-expression denial of service (ReDoS) affects a shared regex-assembly include used to build 12 Unix RCE detection rules in CRS v4, and the same ambiguous pattern was present in the manually-assembled regexes in 4 rules in CRS v3.3. With a single, unauthenticated, crafted request, the generated pattern drives PCRE2 past its backtracking limit. When PCRE2 exceeds that limit, the @rx operator returns an error rather than a match result, which results in detection bypass and CPU denial of service. This issue has been patched in versions 3.3.10, 4.25.1, and 4.28.0.

Severity

CVSS 4.0

8.8 high
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N
EPSS
0.6% estimated probability of exploitation activity in the next 30 days; 49th percentile. Scored 2026-11-13. A forecast for this CVE across the internet, not for your own systems.
CISA's assessment (SSVC)
Exploitation: none · Automatable: yes · Technical impact: partial, assessed 2026-11-12. From CISA's Vulnrichment in the CVE List: whether it is exploited, whether exploiting it can be automated, and how much control it gives.
CWE
CWE-1333 Inefficient Regular Expression Complexity
Published
Modified
Assigned by
GitHub_M (CNA)
NVD analysis
Awaiting analysis
Record from
the NVD, synced

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Affected

Versions

From the CNA's record in the CVE List.

ProductAffected
coreruleset< 3.3.10
coreruleset< 4.25.1
coreruleset< 4.28.0

Linux distributions

DistributionReleasePackageFixed inAdvisory
Debian12, 13, 14modsecurity-crsno fix listedDEBIAN-CVE-2026-61619

From the distributions' data via OSV.dev: the Debian Security Tracker. Modified: reformatted and linked to CVE records. Credits. On the distributions' own pages: Debian.

Attack patterns (CAPEC)

  • CAPEC-492 Regular Expression Exponential Blowup

The attack patterns MITRE's CAPEC relates to this record's weaknesses, as MITRE names them. Credits.

References

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