Predictable Seed in Pseudo-Random Number Generator (PRNG) vulnerability in Mitsubishi Electric Corporation MELSEC iQ-F Series FX5U-xMy/z (x=32,64,80, y=T,R, z=ES,DS,ESS,DSS) with serial number 17X**** or later, and versions 1.280 and prior, Mitsubishi Electric Corporation MELSEC iQ-F Series FX5U-xMy/z (x=32,64,80, y=T,R, z=ES,DS,ESS,DSS) with serial number 179**** and prior, and versions 1.074 and prior, Mitsubishi Electric Corporation MELSEC iQ-F Series FX5UC-xMy/z (x=32,64,96, y=T, z=D,DSS)) with serial number 17X**** or later, and versions 1.280 and prior, Mitsubishi Electric Corporation MELSEC iQ-F Series FX5UC-xMy/z (x=32,64,96, y=T, z=D,DSS)) with serial number 179**** and prior, and versions 1.074 and prior, Mitsubishi Electric Corporation MELSEC iQ-F Series FX5UC-32MT/DS-TS versions 1.280 and prior, Mitsubishi Electric Corporation MELSEC iQ-F Series FX5UC-32MT/DSS-TS versions 1.280 and prior, Mitsubishi Electric Corporation MELSEC iQ-F Series FX5UJ-xMy/z (x=24,40,60, y=T,R, z=ES,ESS) versions 1.042 and prior, Mitsubishi Electric Corporation MELSEC iQ-F Series FX5UJ-xMy/ES-A (x=24,40,60, y=T,R) versions 1.043 and prior, Mitsubishi Electric Corporation MELSEC iQ-F Series FX5S-xMy/z (x=30,40,60,80, y=T,R, z=ES,ESS) versions 1.003 and prior, Mitsubishi Electric Corporation MELSEC iQ-F Series FX5UC-32MR/DS-TS versions 1.280 and prior, Mitsubishi Electric Corporation MELSEC iQ-R Series R00/01/02CPU versions 33 and prior, Mitsubishi Electric Corporation MELSEC iQ-R Series R04/08/16/32/120(EN)CPU versions 66 and prior allows a remote unauthenticated attacker to access the Web server function by guessing the random numbers used for authentication from several used random numbers.
The product uses a Pseudo-Random Number Generator (PRNG) but does not correctly manage seeds.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Fx5u-80mt/ess_firmware | Mitsubishielectric | - (including) | - (including) |
PRNGs are deterministic and, while their output appears
random, they cannot actually create entropy. They rely on
cryptographically secure and unique seeds for entropy so
proper seeding is critical to the secure operation of the
PRNG.
Management of seeds could be broken down into two main areas:
PRNGs require a seed as input to generate a stream of
numbers that are functionally indistinguishable from
random numbers. While the output is, in many cases,
sufficient for cryptographic uses, the output of any
PRNG is directly determined by the seed provided as
input. If the seed can be ascertained by a third party,
the entire output of the PRNG can be made known to
them. As such, the seed should be kept secret and
should ideally not be able to be guessed. For example,
the current time may be a poor seed. Knowing the
approximate time the PRNG was seeded greatly reduces
the possible key space.
Seeds do not necessarily need to be unique, but reusing seeds may open up attacks if the seed is discovered.