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CVE-2026-107845

CRITICAL 9.3

Published 2026-10-09 · Last modified 2026-10-09

Contao is an Open Source CMS. From version 4.0.0 until 5.3.50 and 5.7.12, an unauthenticated visitor can submit a comment whose email or website metadata is rendered without sufficient attribute and URL encoding by listComments() in comments-bundle/contao/dca/tl_comments.php. When a backend user opens the Comments module, attacker-controlled script can execute in the Contao backend origin under that user's session. Unpublished comments remain visible to moderators, so moderation does not prevent exposure. This issue is fixed in versions 5.3.50 and 5.7.12.

ELEVATED IMPACT

Severe if exploited (CVSS 9.3), but no known exploitation and low modeled probability. Patch on a normal cadence.

Exploitation likelihood

0.3%chance of exploitation in 30 days · 20th percentile

○ In CISA KEV ○ Catalogued PoC

Impact if exploited

9.3CVSS 3.1 · CRITICAL

  • ConfidentialityHigh
  • IntegrityHigh
  • AvailabilityNone

What an attacker needs

  • ✓Access: Reachable over the network — no local access needed
  • ✓Privileges: No account or privileges required
  • ⚠User interaction: A user must take an action (click / open a file)
  • ✓Complexity: No special conditions — reliably repeatable

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept

No public PoC is currently catalogued.

Search for new PoCs

Search GitHub now — results may be empty or unverified.

Tracked sources are checked daily for recent CVEs, including PoCs published after the original disclosure. A later release appears after a tracked source lists it and a refresh succeeds.

Data snapshot:

Affected

Vendors Contao

Products Contao

Weakness (CWE)

  • CWE-79: : Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
  • CWE-116: : Improper Encoding or Escaping of Output

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N

References and research data (JSON)

Packages and version ranges

Each advisory describes its own package and affected ranges. A boundary applies to that range; it is not a universal upgrade recommendation.

  • contao/comments-bundle Packagist

    pkg:composer/contao/comments-bundle

    ECOSYSTEM range
    • Introduced version (included): 4.0.0
    • Fixed boundary (excluded): 5.3.50
    391 explicitly listed affected versions

    4.0.0, 4.0.1, 4.0.2, 4.0.3, 4.1.0, 4.1.0-RC1, 4.1.0-beta1, 4.1.1, 4.1.2, 4.10.0, 4.10.0-RC1, 4.10.0-RC2, 4.10.0-RC3, 4.10.0-RC4, 4.10.1, 4.10.2, 4.10.3, 4.10.4, 4.10.5, 4.10.6, 4.10.7, 4.11.0, 4.11.0-RC1, 4.11.0-RC2, 4.11.1, 4.11.2, 4.11.3, 4.11.4, 4.11.5, 4.11.6, 4.11.7, 4.11.8, 4.11.9, 4.12.0, 4.12.0-RC1, 4.12.0-RC2, 4.12.0-RC3, 4.12.1, 4.12.2, 4.12.3, 4.12.4, 4.12.5, 4.12.6, 4.12.7, 4.13.0, 4.13.0-RC1, 4.13.0-RC2, 4.13.0-RC3, 4.13.1, 4.13.10, 4.13.11, 4.13.12, 4.13.13, 4.13.14, 4.13.15, 4.13.16, 4.13.17, 4.13.18, 4.13.19, 4.13.2, 4.13.20, 4.13.21, 4.13.22, 4.13.23, 4.13.24, 4.13.25, 4.13.26, 4.13.27, 4.13.28, 4.13.29, 4.13.3, 4.13.30, 4.13.31, 4.13.32, 4.13.33, 4.13.34, 4.13.35, 4.13.36, 4.13.37, 4.13.38, 4.13.39, 4.13.4, 4.13.40, 4.13.41, 4.13.42, 4.13.43, 4.13.44, 4.13.45, 4.13.46, 4.13.47, 4.13.48, 4.13.49, 4.13.5, 4.13.50, 4.13.51, 4.13.52, 4.13.53, 4.13.54, 4.13.55, 4.13.56, 4.13.57, 4.13.58, 4.13.6, 4.13.7, 4.13.8, 4.13.9, 4.2.0, 4.2.0-RC1, 4.2.0-beta1, 4.2.1, 4.3.0, 4.3.0-RC1, 4.3.1, 4.3.10, 4.3.11, 4.3.2, 4.3.3, 4.3.4, 4.3.5, 4.3.6, 4.3.7, 4.3.8, 4.3.9, 4.4.0, 4.4.0-RC1, 4.4.0-RC2, 4.4.0-beta1, 4.4.1, 4.4.10, 4.4.11, 4.4.12, 4.4.13, 4.4.14, 4.4.15, 4.4.16, 4.4.17, 4.4.18, 4.4.19, 4.4.2, 4.4.20, 4.4.21, 4.4.22, 4.4.23, 4.4.24, 4.4.25, 4.4.26, 4.4.27, 4.4.28, 4.4.29, 4.4.3, 4.4.30, 4.4.31, 4.4.32, 4.4.33, 4.4.34, 4.4.35, 4.4.36, 4.4.37, 4.4.38, 4.4.39, 4.4.4, 4.4.40, 4.4.41, 4.4.42, 4.4.43, 4.4.44, 4.4.45, 4.4.46, 4.4.47, 4.4.48, 4.4.49, 4.4.5, 4.4.50, 4.4.51, 4.4.52, 4.4.53, 4.4.54, 4.4.55, 4.4.56, 4.4.57, 4.4.6, 4.4.7, 4.4.8, 4.4.9, 4.5.0, 4.5.0-RC1, 4.5.0-RC2, 4.5.0-beta1, 4.5.0-beta2, 4.5.0-beta3, 4.5.1, 4.5.10, 4.5.11, 4.5.12, 4.5.13, 4.5.14, 4.5.2, 4.5.3, 4.5.4, 4.5.5, 4.5.6, 4.5.7, 4.5.8, 4.5.9, 4.6.0, 4.6.0-RC1, 4.6.0-RC2, 4.6.0-RC3, 4.6.1, 4.6.10, 4.6.11, 4.6.12, 4.6.13, 4.6.14, 4.6.2, 4.6.3, 4.6.4, 4.6.5, 4.6.6, 4.6.7, 4.6.8, 4.6.9, 4.7.0, 4.7.0-RC1, 4.7.0-RC2, 4.7.0-RC3, 4.7.0-RC4, 4.7.1, 4.7.2, 4.7.3, 4.7.4, 4.7.5, 4.7.6, 4.7.7, 4.8.0, 4.8.0-RC1, 4.8.0-RC2, 4.8.1, 4.8.2, 4.8.3, 4.8.4, 4.8.5, 4.8.6, 4.8.7, 4.8.8, 4.9.0, 4.9.0-RC1, 4.9.0-RC2, 4.9.1, 4.9.10, 4.9.11, 4.9.12, 4.9.13, 4.9.14, 4.9.15, 4.9.16, 4.9.17, 4.9.18, 4.9.19, 4.9.2, 4.9.20, 4.9.21, 4.9.22, 4.9.23, 4.9.24, 4.9.25, 4.9.26, 4.9.27, 4.9.28, 4.9.29, 4.9.3, 4.9.30, 4.9.31, 4.9.32, 4.9.33, 4.9.34, 4.9.35, 4.9.36, 4.9.37, 4.9.38, 4.9.39, 4.9.4, 4.9.40, 4.9.41, 4.9.42, 4.9.5, 4.9.6, 4.9.7, 4.9.8, 4.9.9, 5.0.0, 5.0.0-RC1, 5.0.0-RC2, 5.0.0-RC3, 5.0.0-RC4, 5.0.1, 5.0.10, 5.0.2, 5.0.3, 5.0.4, 5.0.5, 5.0.6, 5.0.7, 5.0.8, 5.0.9, 5.1.0, 5.1.0-RC1, 5.1.0-RC2, 5.1.0-RC3, 5.1.1, 5.1.10, 5.1.11, 5.1.2, 5.1.3, 5.1.4, 5.1.5, 5.1.6, 5.1.7, 5.1.8, 5.1.9, 5.2.0, 5.2.0-RC1, 5.2.0-RC2, 5.2.0-RC3, 5.2.0-RC4, 5.2.0-RC5, 5.2.0-RC6, 5.2.1, 5.2.10, 5.2.2, 5.2.3, 5.2.4, 5.2.5, 5.2.6, 5.2.7, 5.2.8, 5.2.9, 5.3.0, 5.3.0-RC1, 5.3.0-RC2, 5.3.0-RC3, 5.3.0-RC4, 5.3.1, 5.3.10, 5.3.11, 5.3.12, 5.3.13, 5.3.14, 5.3.15, 5.3.16, 5.3.17, 5.3.18, 5.3.19, 5.3.2, 5.3.20, 5.3.21, 5.3.22, 5.3.23, 5.3.24, 5.3.25, 5.3.26, 5.3.27, 5.3.28, 5.3.29, 5.3.3, 5.3.30, 5.3.31, 5.3.32, 5.3.33, 5.3.34, 5.3.35, 5.3.36, 5.3.37, 5.3.38, 5.3.39, 5.3.4, 5.3.40, 5.3.41, 5.3.42, 5.3.43, 5.3.44, 5.3.45, 5.3.46, 5.3.47, 5.3.48, 5.3.49, 5.3.5, 5.3.6, 5.3.7, 5.3.8, 5.3.9

    Additional upstream package constraints
    {
  "database": {
    "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-628f-v4f6-p37r/GHSA-628f-v4f6-p37r.json"
  }
}
    GitHub Advisory Database · GHSA-628f-v4f6-p37r · Updated 2026-10-09T21:00:08.636008908Z
  • contao/comments-bundle Packagist

    pkg:composer/contao/comments-bundle

    ECOSYSTEM range
    • Introduced version (included): 5.4.0-RC1
    • Fixed boundary (excluded): 5.7.12
    71 explicitly listed affected versions

    5.4.0, 5.4.0-RC1, 5.4.0-RC2, 5.4.0-RC3, 5.4.0-RC4, 5.4.1, 5.4.10, 5.4.11, 5.4.12, 5.4.13, 5.4.14, 5.4.2, 5.4.3, 5.4.4, 5.4.5, 5.4.6, 5.4.7, 5.4.8, 5.4.9, 5.5.0, 5.5.0-RC1, 5.5.0-RC2, 5.5.0-RC3, 5.5.0-RC4, 5.5.1, 5.5.10, 5.5.11, 5.5.12, 5.5.13, 5.5.14, 5.5.15, 5.5.16, 5.5.2, 5.5.3, 5.5.4, 5.5.5, 5.5.6, 5.5.7, 5.5.8, 5.5.9, 5.6.0, 5.6.0-RC1, 5.6.0-RC2, 5.6.0-RC3, 5.6.1, 5.6.10, 5.6.11, 5.6.2, 5.6.3, 5.6.4, 5.6.5, 5.6.6, 5.6.7, 5.6.8, 5.6.9, 5.7.0, 5.7.0-RC1, 5.7.0-RC2, 5.7.0-RC3, 5.7.0-RC4, 5.7.1, 5.7.10, 5.7.11, 5.7.2, 5.7.3, 5.7.4, 5.7.5, 5.7.6, 5.7.7, 5.7.8, 5.7.9

    Additional upstream package constraints
    {
  "database": {
    "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-628f-v4f6-p37r/GHSA-628f-v4f6-p37r.json"
  }
}
    GitHub Advisory Database · GHSA-628f-v4f6-p37r · Updated 2026-10-09T21:00:08.636008908Z

All CVSS metrics

  • CRITICAL 9.3 v3.1 · CNA Primary
    CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
  • CRITICAL 9.3 v3.1 · NVD Secondary
    CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N

References

Advisories

Technical & other

Sources: NVD · CVE.org · EPSS