Description
GCHQ CyberChef before 11.0.0 allows XSS via Show Base64 offsets, as demonstrated by the /#recipe=Show_Base64_offsets('%3Cscript substring.
Basic information
- Type
- reviewed
- Severity
- high
- Advisory on GitHub
- Open advisory ↗
- Repository advisory
- —
- Source code
- Browse source ↗
- Published (advisory)
- 2026-04-29 06:33:30 UTC
- Updated
- 2026-05-06 22:09:28 UTC
- GitHub reviewed
- 2026-05-06 22:09:27 UTC
- NVD published
- 2026-04-29
EPSS Score
| Score |
Percentile |
|
0.01%
|
2.11% |
CVSS Scores
| Base score |
Version |
Severity |
Vector |
|
7.2
|
3.1 |
—
|
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
Click to expand
- Attack vector (AV:N)
- Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
- Attack complexity (AC:L)
- Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
- Privileges required (PR:N)
- No account or special rights needed—anonymous or random user is enough.
- User interaction (UI:N)
- Nobody has to click “OK” or open a trap file; it can work without a victim helping.
- Scope (S:C)
- Breaking this can reach past the original component and bite other resources—bigger blast radius.
- Confidentiality (C:L)
- Some sensitive info could get out, but not a total data dump.
- Integrity (I:L)
- Attackers could change some data, but it’s limited—not everything goes.
- Availability (A:N)
- Service keeps running; no real outage angle.
|
CWEs
| CWE id |
Name |
|
CWE-79
|
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') |
Affected packages (1)
Vulnerable version ranges and first patched releases as published by GitHub.
| Ecosystem |
Package |
Vulnerable range |
First patched |
Vulnerable functions |
| npm |
cyberchef |
< 11.0.0 |
11.0.0 |
—
|
cvelogic
Threat Intelligence