{"id":"CVE-2025-6921","title":"The huggingface/transformers library, versions prior to 4.53.0, is vulnerable to Regular Expression Denial of Service (ReDoS) in the AdamWeightDecay optimizer","summary":"The huggingface/transformers library, versions prior to 4.53.0, is vulnerable to Regular Expression Denial of Service (ReDoS) in the AdamWeightDecay optimizer. The vulnerability arises from the _do_use_weight_decay method, which processe…","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-400"],"vendor":"huggingface","product":"transformers","affected":["transformers < 4.53.0"],"patched":["transformers 4.53.0"],"published":"2025-09-23","updated":"2026-10-11","sourceUpdated":"2026-10-11T20:10:00.200","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2025-6921","references":[{"url":"https://github.com/huggingface/transformers/commit/47c34fba5c303576560cb29767efb452ff12b8be","label":"security@huntr.dev"},{"url":"https://huntr.com/bounties/287d15a7-6e7c-45d2-8c05-11e305776f1f","label":"security@huntr.dev"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2025-6921"},{"url":"https://github.com/huggingface/transformers/commit/d37f7517972f67e3f2194c000ed0f87f064e5099"},{"url":"https://github.com/huggingface/transformers"}],"tags":["nvd","osv","pip","score-dispute"],"epss":0.00511,"epssPercentile":0.43364,"aliases":["GHSA-4w7r-h757-3r74","PYSEC-2026-1980"],"ecosystem":"pip","scores":{"nvd":7.5,"osv":5.3},"ingestedAt":"2026-07-08T18:25:45.712Z","slug":"CVE-2025-6921","body":"## Overview\n\nThe huggingface/transformers library, versions prior to 4.53.0, is vulnerable to Regular Expression Denial of Service (ReDoS) in the AdamWeightDecay optimizer. The vulnerability arises from the _do_use_weight_decay method, which processes user-controlled regular expressions in the include_in_weight_decay and exclude_from_weight_decay lists. Malicious regular expressions can cause catastrophic backtracking during the re.search call, leading to 100% CPU utilization and a denial of service. This issue can be exploited by attackers who can control the patterns in these lists, potentially causing the machine learning task to hang and rendering services unresponsive.\n\n## Affected\n\n- `transformers < 4.53.0`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `transformers 4.53.0`\n\n## Package advisory (CVE-2025-6921)\n\nAffected packages:\n\n- `transformers < 4.53.0`\n\nPatched in:\n\n- `transformers 4.53.0`\n\nSource: https://osv.dev/vulnerability/GHSA-4w7r-h757-3r74","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[{"seq":219418,"id":"CVE-2025-6921","ts":1791816730825,"field":"cvss","old":"5.3","new":"7.5"},{"seq":219417,"id":"CVE-2025-6921","ts":1791816730825,"field":"severity","old":"medium","new":"high"}]}