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Qualifier Challenge - KPRCA_00013

Original Versions

Known Vulnerabilities

  • CWE-193 - Off-by-one Error
  • CWE-457 - Use of Uninitialized Variable
  • CWEs are listed as indicated by the challenge author.


  • ForAllSecure: 3.5
  • TECHx: 1.15
  • CSDS: 0.25
  • CodeJitsu: 0.01
  • Disekt: 0.0
  • Shellphish: 0.0
  • FuzzBOMB: 0.0
  • TrailofBits: 0.0
  • DeepRed: 0.0
  • The maximum score for each challenge in CQE is 4, following the CQE Scoring Document.

Passed consensus evaluation

  • CodeJitsu - CB1
  • CSDS - CB1
  • ForAllSecure - CB1
  • Shellphish - CB1
  • TrailofBits - CB1

Proved a POV in reference challenge

Defense against reference POVs

  • CodeJitsu: 100.0% - CB1
  • Shellphish: 100.0% - CB1
  • CSDS: 100.0% - CB1
  • ForAllSecure: 50.0% - CB1
  • TECHx: 50.0% - CB1
  • TrailofBits: 50.0% - CB1

No submission

  • Eighth Place Team
  • Eleventh Place Team
  • Fifth Place Team - Finalist
  • First Place Team - Finalist
  • Fourth Place Team - Finalist
  • Ninth Place Team
  • Second Place Team - Finalist
  • Seventh Place Team - Finalist
  • Sixth Place Team - Finalist
  • Tenth Place Team
  • Third Place Team - Finalist
  • Thirteenth Place Team
  • Twelfth Place Team

All Submissions

DARPA performer group

Kaprica Security (KPRCA)


Accel is a spreadsheet program that enables a user to store information in a table and calculate numerical formulas based on cell data. Similar to other familiar spreadsheet programs, Accel is meant to assist in organizing large amounts of data that have interdependencies. The functions provided will enable a user to complete most simple financial and arithmetic needs.

Feature List

Command Line Operations:

**Literal Assignment A0=1 A0=This is a string

**Formula Assignment A1==SQRT(9) A2==A1+97 A3==SIN(A2/A1)

Supported String Commands:

CLEAR - Clears a cell Accel:-$ CLEAR A3

REPR - Show the representation of a cell (helpful with formulas) Accel:-$ REPR A2 --> =A1+97

SHOW - Show the value of a cell, either literal or computer Accel:-S SHOW A2 --> 100 Accel:-S SHOW A0 --> This is a string

SHOW TABLE - Shows the contents of the entire table Accel:-S SHOW TABLE

EXIT - Exits the program Accel:-S EXIT

Supported Functions:

AVG - Calculate the average of a list COUNT - Count the number of items in a list MAX - Return the largest value in a list MEDIAN - Calculate the median of a list MIN - Return the smallest value in a list STDDEV - Calculate the standard deviation of a list ABS - Return the absolute value of a number COS - Calculate the cosine function of a number LN - Caclualte the natural log of a number LOG10 - Calculate a log base 10 of a number POWER - Raise a number to a power SIN - Calculate the sine function of a number SQRT - Take the square root of a number SUM - Return the summation of a list

Supported Operators

    • Addition
    • Multiplication / - Division
    • Subtraction


In infixtorpn (accel.c:453), an attacker supplied string is parsed into its components. Every time a function name is encountered, it is stored in an array and the index (func_idx) is incremented. The check to test if the array needs to be enlarged is off by one, because the index is incremented between the check and the store. This results in an overflow of the heap buffer, which can allow the attacker to control the heap metadata (size) of the next heap block. Attacker control is limited because the memory is initially set to zero and then incremented every time a comma occurs, but an attacker only needs to get the value to greater than 32 or so to cause a segmentation fault. The fault occurs because the free method will try to split the memory even though it has wrong metadata and overwrite pointers on the heap.

Also, there is an uninitialized variable vulnerability in handle_op_median, where sorted variable wasn't initialized before being cleared.

Generic class of vulnerability

Generic type: Heap-buffer overflow

Uninitialized variable

CWE classification

CWE-193: Off-by-one Error CWE-457: Use of Uninitialized Variable


This cb is meant to be difficult to analyze. The program should provide complexities that are will take some work to reason about. The bug is similar, in that it's difficult to detect what is or isn't a heap overflow especially when dealing with an off-by-one error.

Curated by Lunge Technology, LLC. Questions or comments? Send us email