flex.skl in Will Estes and John Millaway Fast Lexical Analyzer Generator (flex) before 2.5.33 does not allocate enough memory for grammars containing (1) REJECT statements or (2) trailing context rules, which causes flex to generate code that contains a buffer overflow that might allow context-dependent attackers to execute arbitrary code.
| Date Added | Due Date | Vulnerability Name | Required Action |
|---|---|---|---|
| N/A |
| Type | Version | Base score | Base severity | Vector |
|---|---|---|---|---|
| Primary | 2.0 | 7.5 | HIGH | AV:N/AC:L/Au:N/C:P/I:P/A:P |
This issue only affects parsers which are generated by grammars which either use REJECT or rules with a variable trailing context (in these rules the parser has to keep all backtracking paths). The Red Hat Security Response Team analysed all packages that include flex generated parsers in Red Hat Enterprise Linux (2.1, 3, and 4) and found none were vulnerable.