How severe is CVE-2025-6998?

No CVSS score has been assigned to CVE-2025-6998 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2025-6998?

CVE-2025-6998 affects the following packages: calibreweb (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2025-6998?

The records we use list no patched version of calibreweb for CVE-2025-6998. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.

How do I detect CVE-2025-6998 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for calibreweb, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2025-6998 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2025-6998 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-6998 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2025-6998?

CVE-2025-6998 has an EPSS (Exploit Prediction Scoring System) score of 1.0%, placing it in the 62th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2025-6998?

CVE-2025-6998 is classified as CWE-1333 (CWE-1333). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2025-6998 published, and has it been updated?

CVE-2025-6998 was published on July 24, 2025 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2025-6998: calibreweb DoS

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-6998.

EPSS Exploitation Probability

via FIRST.org ↗

1.0%probability of exploitation in next 30 days

Lower Risk+0.12%

Lower risk than most CVEs62th percentile — riskier than 62% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐍calibreweb

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

ReDoS in strip_whitespaces() function in cps/string_helper.py in Calibre Web and Autocaliweb allows unauthenticated remote attackers to cause denial of service via specially crafted username parameter that triggers catastrophic backtracking during login. This issue affects Calibre Web: 0.6.24 (Nicolette); Autocaliweb: from 0.7.0 before 0.7.1.

Affected Packages

1 total

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`calibreweb`	all versions	No fix

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for calibreweb, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
The records we use list no patched version of calibreweb for CVE-2025-6998. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.
Mitigate without a patch
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

ReDoS in strip_whitespaces() function in cps/string_helper.py in Calibre Web and Autocaliweb allows unauthenticated remote attackers to cause denial of service via specially crafted username parameter that triggers catastrophic backtracking during login. This issue affects Calibre Web: 0.6.24 (Nicolette); Autocaliweb: from 0.7.0 before 0.7.1.

O3 Security · Impact-Aware SCA

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CVE-2025-6998 — calibreweb