CVE-2026-49477: Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4

Q: How do I fix CVE-2026-49477?

soup sieve: upgrade to 2.8.4. Exact commands for each OS are on this page.

Q: Is CVE-2026-49477 being exploited?

CVE-2026-49477 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-49477 affect?

CVE-2026-49477 affects soup sieve. Severity is high (CVSS 7.5). 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

Q: How urgent is CVE-2026-49477?

Priority 49/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 7.5REMOTEUPGRADE

CVE-2026-49477 is a high-severity flaw (CVSS 7.5) affecting soup sieve. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 50%)
CISA exploited list	No
Weakness	CWE-400, CWE-1333
Published	2026-07-14
Last modified	2026-10-24

Publisher (CNA): GitHub, Inc. · Vendor: facelessuser

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-14 21:17 UTCPublished CVE record published
2026-10-24 21:10 UTCUpdated Record last modified

facelessuser soup sieve UPGRADE

Affected: < 2.8.4

Fixed in: 2.8.4

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy soup-sieve || rpm -q soup-sieve || soup-sieve --version

2. UPGRADE to 2.8.4 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade soup-sieve

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade soup-sieve

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-49477?

soup sieve: upgrade to 2.8.4. Exact commands for each OS are on this page.

Is CVE-2026-49477 being exploited?

CVE-2026-49477 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-49477 affect?

CVE-2026-49477 affects soup sieve. Severity is high (CVSS 7.5). 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

How urgent is CVE-2026-49477?

Priority 49/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-49476 HIGH 7.5 UPGRADE Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4

References

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