CVE-2025-6998Public exploitNetwork attack vector

Unauthenticated service hang via username regex backtracking

Published Jul 24, 2025 · Updated Jul 25, 2025

Regular expression denial of service in Calibre-Web 0.6.24 and Autocaliweb 0.7.0 allows remote attackers to hang the service during login. The strip_whitespaces() function in cps/string_helper.py applies a backtracking-prone regular expression directly to the username and rate-limit key. An unauthenticated crafted username consumes backend processing long enough to interrupt availability, without reported data exposure or modification.

CVSS severity8.7
High
EPSS probability0.83%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Regular expression denial of service in Calibre-Web 0.6.24 and Autocaliweb 0.7.0 allows remote attackers to hang the service during login. The strip_whitespaces() function in cps/string_helper.py applies a backtracking-prone regular expression directly to the username and rate-limit key. An unauthenticated crafted username consumes backend processing long enough to interrupt availability, without reported data exposure or modification.

The record

CVE
CVE-2025-6998
Published
Jul 24, 2025
Updated
Jul 25, 2025
Vendor
Calibre-Web
Product
Calibre-Web
Classifications
CWE-1333, CAPEC-492, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 24, 2025CVE publishedPublication date reported by the CVE source.
  2. Jul 25, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0.6.24

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Calibre-Web · Calibre-Webversion=0.6.24
gelbphoenix · Autocaliwebversion=0.7.0 <0.7.1

Published CVSS scores

8.7Fluid AttacksCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1333Inefficient Regular Expression Complexity
CAPEC-492Regular Expression Exponential Blowup
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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