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Fencer Vulns
low 3.5

CVE-2026-24048 json

Backstage has a Possible SSRF when reading from allowed URL's in `backend.reading.allow`

published 2026-01-21 9 mo ago modified 2026-06-17 4 mo ago also EUVD-2026-4136 , GHSA-q2x5-4xjx-c6p9

cvss
3.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 14%
public exploits
0
none known

Summary

Backstage is an open framework for building developer portals, and @backstage/backend-defaults provides the default implementations and setup for a standard Backstage backend app. Prior to versions 0.12.2, 0.13.2, 0.14.1, and 0.15.0, the `FetchUrlReader` component, used by the catalog and other plugins to fetch content from URLs, followed HTTP redirects automatically. This allowed an attacker who controls a host listed in `backend.reading.allow` to redirect requests to internal or sensitive URLs that are not on the allowlist, bypassing the URL allowlist security control. This is a Server-Side Request Forgery (SSRF) vulnerability that could allow access to internal resources, but it does not allow attackers to include additional request headers. This vulnerability is fixed in `@backstage/backend-defaults` version 0.12.2, 0.13.2, 0.14.1, and 0.15.0. Users should upgrade to this version or later. Some workarounds are available. Restrict `backend.reading.allow` to only trusted hosts that you control and that do not issue redirects, ensure allowed hosts do not have open redirect vulnerabilities, and/or use network-level controls to block access from Backstage to sensitive internal endpoints.

Patch / fix

  • npm @backstage/backend-defaults 0.12.2, 0.13.2, 0.14.1
  • linuxfoundation @backstage/backend-defaults 0.12.2, 0.13.2, 0.14.1
  • linuxfoundation backstage/backend_defaults 0.12.2, 0.13.2, 0.14.1
  • linuxfoundation backstage_backend-defaults 0.12.2, 0.13.2, 0.14.1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-24048 updated cvss 3.5

@backstage/backend-defaults: Backstage SSRF when reading from allowed URL's in `backend.reading.allow`

  • Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9
    affected: workaround, no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
9 mo ago

Exploit prediction

0.24% chance of exploitation in the next 30 days, higher than 14% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 3.5 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:N/A:N
GitHub 3.1 3.5 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:N/A:N
NVD 3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Affected packages

ecosystem package affected fixed in
npm @backstage/backend-defaults
<0.12.2
>=0.13.0, <0.13.2
>=0.14.0, <0.14.1
0.12.2
0.13.2
0.14.1

Affected products

  • backstage backstage

Classification

Weakness
  • CWE-918 Server-Side Request Forgery

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.