js-yaml is a JavaScript YAML parser and dumper. From 3.0.0 until 3.15.2 and 4.3.2, maxTotalMergeKeys in lib/js-yaml/loader.js and lib/loader.js does not count empty mapping sources while processing the merge key <<. An attacker can alias a large sequence of empty mappings into many merge targets, causing O(N * K) processing while totalMergeKeys remains unchanged and the configured resource limit is never reached.
A relatively small YAML document can therefore cause prolonged CPU consumption in applications that parse untrusted YAML, and merge processing is enabled by default on these release lines. This issue is fixed in versions 3.15.2 and 4.3.2.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
High
Complete denial of service
CVSS Vector v3.1
Weakness Type (CWE)
Vulnerable Products
nodeca:js-yaml
References 7
https://github.com/nodeca/js-yaml/security/advisories/GHSA-2883-xcg3-v3hh
https://github.com/nodeca/js-yaml/security/advisories/GHSA-2883-xcg3-v3hh
https://github.com/nodeca/js-yaml/pull/797
https://github.com/nodeca/js-yaml/pull/797
https://github.com/nodeca/js-yaml/commit/3485bc06ff8a0251505f44a00414d90df24666…
https://github.com/nodeca/js-yaml/commit/3485bc06ff8a0251505f44a00414d90df2466639
https://github.com/nodeca/js-yaml/commit/6a8e05f9a485188ed730ac81e81ae221352ef4…
https://github.com/nodeca/js-yaml/commit/6a8e05f9a485188ed730ac81e81ae221352ef480
https://github.com/nodeca/js-yaml/commit/d90b6612a5a84385bdcb556c44578eac76dc0f…
https://github.com/nodeca/js-yaml/commit/d90b6612a5a84385bdcb556c44578eac76dc0f6b
https://github.com/nodeca/js-yaml/releases/tag/3.15.2
https://github.com/nodeca/js-yaml/releases/tag/3.15.2
https://github.com/nodeca/js-yaml/releases/tag/4.3.2
https://github.com/nodeca/js-yaml/releases/tag/4.3.2