Regular expression backtracking in CallBackery request path handling
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA. Impact type from CWE-1333.
Summary
CallBackery versions before 0.62.0 for Perl allow denial of service because the request path is interpolated unquoted as a regular expression under CGI, FastCGI and PSGI. The before_dispatch hook installed by startup() strips PATH_INFO from the request URI using a substitution, and the client controls both the pattern and the string it is matched against. An unauthenticated remote attacker can send a short request with a backreference in the path, which backtracks exponentially and can keep a worker process busy for minutes (CWE-1333).
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
Description from the CNA
CallBackery versions before 0.62.0 for Perl allow denial of service via the request path interpolated as a regular expression under CGI, FastCGI and PSGI. The before_dispatch hook installed by startup() removes PATH_INFO from the end of the request URI with a substitution that interpolates PATH_INFO unquoted. Under CGI, FastCGI and PSGI both values come from the request, so the client chooses both the pattern and the string it is matched against. A short unauthenticated request with a backreference in the path backtracks exponentially and can keep a worker process busy for minutes.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | CallBackery | before 0.62.0 | 0.62.0 | Patch available | CNA |
- CallBackery Vendor— Affected before 0.62.0 Fixed in 0.62.0 Patch available CNA
Remediation
Upgrade CallBackery to version 0.62.0 or later.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
- Fix · CNA CallBackery Fixed in 0.62.0
Timeline
- 2026-10-30 Threatist record created from CVE-2026-118993
- 2026-10-30 Alias added: GHSA-w6qp-45h2-h9fh
- 2026-11-06 CVSS score added · CISA ADP
- 2026-11-06 CISA SSVC decision points changed
References
Sources
- CVE-2026-118993 · CVE Program
- CVE-2026-118993 · NVD
- FIRST EPSS
- GHSA-w6qp-45h2-h9fh · GitHub Advisory Database · CC BY 4.0
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