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Inefficient Regular Expression Complexity


Severity High
Score 7.5/10


A regular expression based DoS vulnerability in Action Dispatch related to the "If-None-Match" header. This vulnerability affects versions through, 6.x through 6.1.7, and 7.x through 7.0.4. A specially crafted HTTP "If-None-Match" header can cause the regular expression engine to enter a state of catastrophic backtracking, when on a version of Ruby below 3.2.0. This can cause the process to use large amounts of CPU and memory, leading to a possible DoS vulnerability. All users running an affected release should either upgrade or use one of the workarounds immediately.

  • LOW
  • NONE
  • NONE
  • NONE
  • NONE
  • HIGH

CWE-1333 - Inefficient Regular Expression Complexity

The product uses a regular expression with an inefficient, possibly exponential worst-case computational complexity that consumes excessive CPU cycles.

Advisory Timeline

  • Published