CVE-2026-25540

MEDIUMNVD 6.56.5—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.5 under NVD CVSS v3. EPSS exploit probability: 0.0%, top 91% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
6.5
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 6.5Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Mastodon is a free, open-source social network server based on ActivityPub. Prior to versions 4.3.19, 4.4.13, 4.5.6, Mastodon is vulnerable to web cache poisoning via `Rails.cache. When AUTHORIZED_FETCH is enabled, the ActivityPub endpoints for pinned posts and featured hashtags have contents that depend on the account that signed the HTTP request. However, these contents are stored in an internal cache and reused with no regards to the signing actor. As a result, an empty response generated for a blocked user account may be served to requests from legitimate non-blocked actors, or conversely, content intended for non-blocked actors may be returned to blocked actors. This issue has been patched in versions 4.3.19, 4.4.13, 4.5.6.

CVSS v3
6.5
EG Score
6.5(medium)
EPSS
31.9%
KEV
Not listed

Published

February 4, 2026

Last Modified

February 20, 2026

References (1)

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 12× in last 7d / 50× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-22 14:08 UTCEPSS rescore
  2. 2026-07-21 15:24 UTCEPSS rescore
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  4. 2026-07-20 17:08 UTCEPSS rescore
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  18. 2026-07-13 08:07 UTCOSV refresh
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  1. 2026-07-08 15:15 UTCEPSS rescore
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  3. 2026-07-06 16:27 UTCEPSS rescore
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  5. 2026-07-06 02:23 UTCEPSS rescore
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  7. 2026-07-05 02:30 UTCEPSS rescore
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  19. 2026-06-25 13:49 UTCEPSS rescore
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  21. 2026-06-24 22:01 UTCOSV refresh
  22. 2026-06-24 14:05 UTCEPSS rescore
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  24. 2026-06-23 21:33 UTCEPSS rescore
  25. 2026-06-23 21:32 UTCEPSS rescore
  26. 2026-06-22 14:25 UTCEPSS rescore
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  28. 2026-06-21 14:56 UTCEPSS rescore
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  40. 2026-06-13 23:00 UTCEPSS rescore
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  44. 2026-06-10 22:18 UTCEPSS rescore
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  47. 2026-06-08 14:17 UTCEPSS rescore
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  49. 2026-06-07 15:25 UTCEPSS rescore
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  52. 2026-06-06 13:47 UTCEPSS rescore
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  66. 2026-05-31 00:16 UTCEPSS rescore
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  68. 2026-05-29 14:35 UTCEG score recompute
  69. 2026-05-29 13:44 UTCEPSS rescore
  70. 2026-05-29 13:44 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2026-25540?
CVE-2026-25540 is a medium vulnerability published on February 4, 2026. Mastodon is a free, open-source social network server based on ActivityPub. Prior to versions 4.3.19, 4.4.13, 4.5.6, Mastodon is vulnerable to web cache poisoning via `Rails.cache. When AUTHORIZED_FETCH is enabled, the ActivityPub endpoints for pinned posts and featured hashtags have contents that…
When was CVE-2026-25540 disclosed?
CVE-2026-25540 was first published in the National Vulnerability Database on February 4, 2026, with the most recent update on February 20, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-25540 actively exploited?
CVE-2026-25540 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 31.9% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-25540?
CVE-2026-25540 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2026-25540?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-25540, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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