CVE-2026-49477: Soup Sieve · Regular Expression Denial of Service (ReDoS) via Selector Parser
Affects jupyterlabSource GCVE Database
Not known to be exploited · CVSS 7.5 High : upgrade to 4.5.8 soon.
Data as of 30 Oct 2026, 08:59 UTC
- Patch
- Available – fixed in 4.5.8
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 13 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.
What to do
Upgrade jupyterlab to 4.5.8.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Homebrewjupyterlabpkg:brew/jupyterlabOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A patch is available in soupsieve version 4.5.8 that fixes the regex pattern to prevent catastrophic backtracking. Users should upgrade to version 4.5.8 or later. Until patched, avoid passing untrusted or user-supplied CSS selectors to soupsieve.compile() or Beautiful Soup's select/select_one methods. Employ input validation or sanitization to reject unterminated quoted selectors if upgrading is not immediately possible.
Description
A Regular Expression Denial of Service (ReDoS) vulnerability exists in soupsieve's CSS selector parser due to a regex pattern that suffers from catastrophic backtracking when processing unterminated quoted attribute selectors. This flaw allows an attacker to cause CPU exhaustion by submitting a crafted CSS selector string with an unterminated quote, leading to exponential regex backtracking and thread blocking. The vulnerability affects applications using soupsieve.compile() or Beautiful Soup's select methods with untrusted input. A fix is available in soupsieve version 4.5.8.