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python · bleachHeads-up

bleach 6.3.0: ReDoS via email linkification in EMAIL_RE

Bleach 6.3.0 exposes a documented email-linkification path that can cause multi-second CPU consumption per request when processing attacker-controlled non-email

17 Jun 2026Read 1 minSeverity: schedule it

What changed

Bleach 6.3.0 exposes a documented email-linkification path that can cause multi-second CPU consumption per request when processing attacker-controlled non-email text of around 30 KB, due to inefficient regular expression complexity in EMAIL_RE.

Who it affects

Applications using bleach.linkify with parse_email=True on user-submitted text, especially those without input length limits or request timeouts.

What to do today

Disable parse_email=True or apply input length limits and request timeouts until a patch is available.

The trail
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