CVE-2026-74583

UNRATEDCVSS · not yet scoredTrending — 3 sources updated this week
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EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • No CVSS published and no exploitation signals yet
CISA-KEV: Not listedEPSS PROB: —CVSS v2: —Exploit: None knownExposed: 0

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

In the Linux kernel, the following vulnerability has been resolved:

net/sched: cls_route: fix fastmap use-after-free on filter

The route4 classifier maintains a 16-slot fastmap cache that stores raw struct route4_filter pointers indexed by (id, iif). The reader (route4_classify) populates this cache via route4_set_fastmap() for every classified packet that hits a filter. The writer (route4_delete, route4_change) clears the cache via route4_reset_fastmap() before RCU-deferred kfree of the filter.

This creates a UAF race:

  • Reader walks the RCU-protected bucket chain, finds filter f
  • Writer unlinks f, calls route4_reset_fastmap(), then tcf_queue_work()
  • Reader calls route4_set_fastmap() and writes f into the cache
*after* the writer's reset, caching a pointer about to be freed
  • After the RCU grace period, kfree(f) executes
  • Next classified packet on the same (id, iif) tuple hits the stale
fastmap entry and reads f->res from freed memory

Reproduced with an mdelay(100) accelerator in route4_set_fastmap() and a concurrent add/delete stress test (provided by both zdi and Santosh). Both triggered KASAN slab-use-after-free reports in the route4 fastmap paths.

Fix: Introduce a per-filter boolean dying flag to suppress stale fastmap republishing by in-flight readers.

CVSS v3
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EchelonGraph score
Not yet assessedNo source has published severity data for this CVE yet — no CVSS score from NVD or a CNA, no GitHub advisory, and it is not in CISA KEV. This is not a rating of zero; we cannot assess it yet.
EG Score
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EG Risk
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EPSS PROB
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EPSS %ILE
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KEV
Not listed

Published

August 21, 2026

Last Modified

August 21, 2026

References (8)

Vendor Advisories for CVE-2026-74583(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Data Freshness Timeline

(refreshed 3× in last 7d / 3× 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. 2026-08-21 17:21 UTCNVD update
  2. 2026-08-21 16:51 UTCEG score recompute
  3. 2026-08-21 16:49 UTCMITRE cvelistV5first tracked

Frequently asked(3)

What is CVE-2026-74583?
CVE-2026-74583 is a publicly disclosed vulnerability published on August 21, 2026. In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_route: fix fastmap use-after-free on filter The route4 classifier maintains a 16-slot fastmap cache that stores raw struct route4_filter pointers indexed by (id, iif). The reader (route4classify) populates this cache…
When was CVE-2026-74583 disclosed?
CVE-2026-74583 was first published in the National Vulnerability Database on August 21, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
How do I remediate CVE-2026-74583?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-74583, 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.

Dependency Blast Radius

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