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Fencer Vulns
medium 5.1

CVE-2026-42259 json

Saltcorn: Open Redirect in `POST /auth/login` due to incomplete `is_relative_url` validation (backslash bypass)

published 2026-04-16 6 mo ago modified 2026-06-17 4 mo ago also EUVD-2026-28431 , GHSA-f3g8-9xv5-77gv

cvss
5.1
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 27%
public exploits
0
none known

Summary

Saltcorn is an extensible, open source, no-code database application builder. Prior to versions 1.4.6, 1.5.6, and 1.6.0-beta.5, Saltcorn validates the post-login dest parameter with a string check that only blocks :/ and //. Because all WHATWG-compliant browsers normalise backslashes (\) to forward slashes (/) for special schemes, a payload such as /\evil.com/path slips through is_relative_url(), is emitted unchanged in the HTTP Location header, and causes the browser to navigate cross-origin to an attacker-controlled domain. The bug is reachable on a default install and only requires a victim who can be tricked into logging in via a crafted Saltcorn URL. This issue has been patched in versions 1.4.6, 1.5.6, and 1.6.0-beta.5.

Patch / fix

  • npm @saltcorn/server 1.4.6, 1.5.6, 1.6.0-beta.5
  • saltcorn saltcorn 1.4.6, 1.5.6, 1.6.0-beta.5

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
6 mo ago

Exploit prediction

0.34% chance of exploitation in the next 30 days, higher than 27% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/saltcorn/saltcorn/security/advisories/GHSA-f3g8-9xv5-77gv referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 5.1 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
CNA 4.0 5.1 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected packages

ecosystem package affected fixed in
npm @saltcorn/server
<1.4.6
>=1.5.0-beta.0, <1.5.6
>=1.6.0-alpha.0, <1.6.0-beta.5
1.4.6
1.5.6
1.6.0-beta.5

Affected products

  • saltcorn saltcorn

Classification

Weakness
  • CWE-601 URL Redirection to Untrusted Site

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.