Reject SafeMarshal collection lengths longer than the remaining input - #9756
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Reject SafeMarshal collection lengths longer than the remaining input#9756hsbt wants to merge 1 commit into
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A crafted 4-byte length makes read_array and its siblings allocate the Array.new backing store before reading a single element, so an 8-byte payload can request gigabytes of memory (HackerOne 3877678, triaged as hardening). Since every element consumes at least one byte, a count larger than the remaining input bytes can never be valid. Raise the new LengthTooLongError instead of allocating, and add the negative length check that read_hash was missing. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Gem::SafeMarshal::Reader#read_integercan decode a 4-byte length of up to about 4.3 billion, andread_array,read_hash,read_hash_with_default_value,read_object_with_ivars, andread_objectpassed that length straight toArray.new, which allocates the backing store before any element is read. An 8-byte payload is enough to raiseNoMemoryError. Reported in HackerOne 3877678 and triaged as hardening rather than a vulnerability.Since every marshal element consumes at least one byte of input, a declared count larger than the bytes remaining in the stream can never be valid. This adds a
read_counthelper that raises the newLengthTooLongErrorin that case, and also adds the negative length check thatread_hashwas missing. Legitimate inputs are unaffected because the bound is derived from the input itself rather than a magic constant.