Soup Sieve: Regular Expression Denial of Service (ReDoS) in soupsieve Selector Parser
Priority HIGH 72CWE-1333Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 10 fixed, 6 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-1333.
Summary
Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4. Prior to 2.8.4, the CSS selector parser in soupsieve contains a regular expression vulnerable to catastrophic backtracking when processing an attribute selector with an unterminated quoted value in soupsieve/css_parser.py, allowing an attacker who can supply untrusted CSS selector strings to soupsieve.compile() or Beautiful Soup .select() / .select_one() to cause CPU exhaustion and denial of service. This issue is fixed in version 2.8.4.
Why it matters now
Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00644 51st percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Partial soupsieve (facelessuser): 2.8.4soupsieve (PyPI): 2.8.4Red Hat: 10 advisoriesRed Hat: 10 fixed, 6 without a fix
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| facelessuser | soupsieve | before 2.8.4 | 2.8.4 | Patch available | CNA |
| — | soupsieve (PyPI) | before 2.8.4 | 2.8.4 | Patch available | GHSA-836r-79rf-4m37 |
- soupsieve Vendorfacelessuser Affected before 2.8.4 Fixed in 2.8.4 Patch available CNA
- soupsieve (PyPI) Vendor— Affected before 2.8.4 Fixed in 2.8.4 Patch available GHSA-836r-79rf-4m37
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:facelessuser:soup_sieve:*:*:*:*:*:beautiful_soup:*:* | before 2.8.4 | Vulnerable | facelessuser |
- cpe:2.3:a:facelessuser:soup_sieve:*:*:*:*:*:beautiful_soup:*:* Versions before 2.8.4 Vulnerable ·facelessuser
Remediation
- Fix · CNA soupsieve (facelessuser) Fixed in 2.8.4
- Fix · GHSA-836r-79rf-4m37 soupsieve (PyPI) Fixed in 2.8.4 Advisory →
Red Hat 10 advisories
- RHSA-2026:81110 Released 2026-10-12 · Red Hat rating ImportantRed Hat Quay 3.18.1
- Red Hat Quay 3.18 registry.redhat.io/quay/quay-builder-rhel9, registry.redhat.io/quay/quay-rhel9
- RHSA-2026:74511 Released 2026-10-01 · Red Hat rating ImportantRed Hat Quay 3.17.5
- Red Hat Quay 3.17 registry.redhat.io/quay/quay-rhel9
- RHSA-2026:70267 Released 2026-09-22 · Red Hat rating ImportantRed Hat Quay 3.14.9
- Red Hat Quay 3.14 registry.redhat.io/quay/quay-rhel8
Show 7 more Red Hat advisories
- RHSA-2026:69255 Released 2026-09-21 · Red Hat rating ImportantRed Hat Quay 3.16.6
- Red Hat Quay 3.16 registry.redhat.io/quay/quay-rhel9
- RHSA-2026:66523 Released 2026-09-10 · Red Hat rating ImportantRed Hat Quay 3.12.22
- Red Hat Quay 3.12 registry.redhat.io/quay/quay-rhel8
- RHSA-2026:66084 Released 2026-09-09 · Red Hat rating ImportantRed Hat Quay 3.10.26
- Red Hat Quay 3.10 registry.redhat.io/quay/quay-rhel8
- RHSA-2026:65514 Released 2026-09-08 · Red Hat rating ImportantRed Hat Quay 3.9.26
- Red Hat Quay 3.9 registry.redhat.io/quay/quay-rhel8
- RHSA-2026:63307 Released 2026-09-03 · Red Hat rating ImportantRed Hat Quay 3.15.8
- Red Hat Quay 3.15 registry.redhat.io/quay/quay-builder-rhel8, registry.redhat.io/quay/quay-rhel8
- RHSA-2026:60520 Released 2026-08-27 · Red Hat rating CriticalRHOAI 3.4.4 - Red Hat OpenShift AI
- Red Hat OpenShift AI 3.4 registry.redhat.io/rhoai/odh-automl-rhel9, registry.redhat.io/rhoai/odh-autorag-rhel9, registry.redhat.io/rhoai/odh-built-in-detector-rhel9 +47
- RHSA-2026:34119 Released 2026-07-01 · Red Hat rating ImportantRed Hat Hardened Images RPMs bug fix and enhancement update
- Red Hat Hardened Images python-rpds-py-2026.6.3-1.hum1@src, python3-rpds-py-2026.6.3-1.hum1@aarch64, python3-rpds-py-2026.6.3-1.hum1@x86_64
Vendor assessments
Red Hat
Red Hat rating: Important. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Exploit Intelligence | Affected | No fix yet |
| Lightspeed Core | Affected | No fix yet |
| Red Hat Ansible Automation Platform 2 | Affected | No fix planned: Will not fix |
| Red Hat OpenShift AI (RHOAI) | Affected | No fix yet |
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet |
| Red Hat OpenShift Virtualization 4 | Affected | No fix yet |
| Red Hat Hardened Images | Fixed | RHSA-2026:34119 |
| Red Hat OpenShift AI 3.4 | Fixed | RHSA-2026:60520 |
| Red Hat Quay 3.10 | Fixed | RHSA-2026:66084 |
| Red Hat Quay 3.12 | Fixed | RHSA-2026:66523 |
| Red Hat Quay 3.14 | Fixed | RHSA-2026:70267 |
| Red Hat Quay 3.15 | Fixed | RHSA-2026:63307 |
| Red Hat Quay 3.16 | Fixed | RHSA-2026:69255 |
| Red Hat Quay 3.17 | Fixed | RHSA-2026:74511 |
| Red Hat Quay 3.18 | Fixed | RHSA-2026:81110 |
| Red Hat Quay 3.9 | Fixed | RHSA-2026:65514 |
Not affected: 14 products
- Lightspeed Core
- Migration Toolkit for Applications 8
- OpenShift Lightspeed
- Red Hat Hardened Images
- Red Hat OpenShift AI (RHOAI)
- Red Hat OpenShift AI 3.4
- Red Hat Quay 3.10
- Red Hat Quay 3.12
- Red Hat Quay 3.14
- Red Hat Quay 3.15
- Red Hat Quay 3.16
- Red Hat Quay 3.17
- Red Hat Quay 3.18
- Red Hat Quay 3.9
Timeline
- 2026-10-02 Threatist record created from CVE-2026-49477
- 2026-10-03 Alias added: GHSA-836r-79rf-4m37
- 2026-10-13 Fix available: RHSA-2026:81110 · Red Hat
- 2026-10-13 Fix available: Red Hat Quay 3.18 · Red Hat
- 2026-10-21 EPSS moved to the 50th–90th percentile
- 2026-11-03 Affected versions changed · Red Hat
References
More facelessuser Soup Sieve vulnerabilities
- TI-2026-36630 Soup Sieve: Memory Exhaustion via Large Comma-Separated Selector Lists in soupsieve CVSS 3.1HIGH 7.5
Sources
- CVE-2026-49477 · CVE Program
- CVE-2026-49477 · NVD
- FIRST EPSS
- GHSA-836r-79rf-4m37 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-49477 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences