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Fencer Intel
medium 6.7

CVE-2025-31136 json

FreshRSS vulnerable to Cross-site Scripting by <iframe>'ing a vulnerable same-origin page in a feed entry

published last yr. modified 4mo ago also EUVD-2025-16906

cvss
6.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 33%
public exploits
0
none known

Summary

FreshRSS is a self-hosted RSS feed aggregator. Prior to version 1.26.2, it's possible to run arbitrary JavaScript on the feeds page. This occurs by combining a cross-site scripting (XSS) issue that occurs in `f.php` when SVG favicons are downloaded from an attacker-controlled feed containing `<script>` tags inside of them that aren't sanitized, with the lack of CSP in `f.php` by embedding the malicious favicon in an iframe (that has `sandbox="allow-scripts allow-same-origin"` set as its attribute). An attacker needs to control one of the feeds that the victim is subscribed to, and also must have an account on the FreshRSS instance. Other than that, the iframe payload can be embedded as one of two options. The first payload requires user interaction (the user clicking on the malicious feed entry) with default user configuration, and the second payload fires instantly right after the user adds the feed or logs into the account while the feed entry is still visible. This is because of lazy image loading functionality, which the second payload bypasses. An attacker can gain access to the victim's account by exploiting this vulnerability. If the victim is an admin it would be possible to delete all users (cause damage) or execute arbitrary code on the server by modifying the update URL using fetch() via the XSS. Version 1.26.2 has a patch for the issue.

Patch / fix

  • freshrss freshrss 1.26.2

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CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
total
Assessed
last yr.

Exploit prediction

0.39% chance of exploitation in the next 30 days, higher than 33% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • github.com https://github.com/FreshRSS/FreshRSS/security/advisories/GHSA-f6r4-jrvc-cfmr referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 6.7 CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:L
NVD 3.1 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Affected products

  • FreshRSS FreshRSS

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation

References

Sources

Fencer Intel 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.