vulnerability / NVI-00014098 / Revision 2
Soup Sieve: Polynomial-time ReDoS (O(n²)) in the `IDENTIFIER` / `VALUE` selector sub-patterns
GitHub lists this reviewed advisory for soupsieve. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
5.3 medium
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
0.609%
FIRST EPSS model v2026.06.15; exploitation probability over 30 days, percentile 0.49211. Missing scores are unknown.
As of · FIRST EPSS
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
soupsieve
source listed< 2.9.0
## Summary soupsieve compiles CSS selector strings with a set of hand-written regular expressions. The shared `IDENTIFIER` sub-pattern (also embedded in `VALUE`, and therefore in attribute selectors) places two adjacent quantified groups over overlapping character classes: `(?:[classA]|ESC)+(?:[classB]|ESC)*`, where both classes match ordinary identifier characters such as `a`. When a selector contains a long identifier/value run that must ultimately fail to match (e.g. an attribute value with no closing `]`, or an identifier followed by an invalid character), the regex engine backtracks across all O(n) ways to split the run between the `+` group and the `*` group, giving O(n²) parse time. A single attacker-controlled selector of a few kilobytes stalls the interpreter for many seconds of CPU; tens of kilobytes reach minutes. ## Trust model (Q0) The selector string is the input. It reaches this code via `soupsieve.compile()`, `soupsieve.select/iselect/match/filter`, and — most commonly — BeautifulSoup's `soup.select(selector)` / `soup.select_one(selector)`, which delegate to soupsieve. This is exploitable in any application that passes a user-controlled CSS selector to BeautifulS
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. FIRST EPSS
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-gjv8-xp57-g29c ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
- CVE-2026-86000 ↗
FIRST EPSS · official catalog
Observed . FIRST EPSS; probability of exploitation in the next 30 days, not local compromise. Dataset date/model retained; FIRST services terms apply.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 2 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.