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VulnerabilityPublished

CVE-2026-42615: GCHQ CyberChef · XSS or 'Cross-site Scripting'

Affects GCHQ CyberChefSource CVE Database V5

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Not known to be exploited · CVSS 7.2 High : upgrade to 11.0.0 soon.

Data as of 29 Oct 2026, 07:15 UTC

CVSS 3.1 base score
7.2High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 22% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 11.0.0
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 29 Apr 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade CyberChef and gchq/CyberChef to 11.0.0.

Affected software

ProductAffectedFixed in
GCHQCyberChefAffected
  • <11.0.0
Fixed in
  • 11.0.0
GitHubgchq/CyberChefpkg:github/gchq/CyberChefOther threatsAffected
  • <11.0.0
Fixed in
  • 11.0.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, avoid using affected versions of CyberChef with untrusted input, especially the Show Base64 offsets feature. Implement additional input validation or sanitization on the client side if possible.

Description

GCHQ CyberChef before 11.0.0 allows XSS via Show Base64 offsets, as demonstrated by the /#recipe=Show_Base64_offsets('%3Cscript substring.

References

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