CVE-2025-21809

MEDIUMNVD 5.55.5
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to NVD's CVSS score.

Score 5.5 from GitHub Security Advisory published 2025-02-27. NVD baseline CVSS 5.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, NVD CVSS v3

Also known asEUVD-2025-5999 (ENISA EUVD) · GHSA-4fj4-ghwr-gjf7 (GitHub Security Advisories)Source: ENISA EUVD

5.5EG
EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 5.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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

rxrpc, afs: Fix peer hash locking vs RCU callback

In its address list, afs now retains pointers to and refs on one or more rxrpc_peer objects. The address list is freed under RCU and at this time, it puts the refs on those peers.

Now, when an rxrpc_peer object runs out of refs, it gets removed from the peer hash table and, for that, rxrpc has to take a spinlock. However, it is now being called from afs's RCU cleanup, which takes place in BH context - but it is just taking an ordinary spinlock.

The put may also be called from non-BH context, and so there exists the possibility of deadlock if the BH-based RCU cleanup happens whilst the hash spinlock is held. This led to the attached lockdep complaint.

Fix this by changing spinlocks of rxnet->peer_hash_lock back to BH-disabling locks.

================================ WARNING: inconsistent lock state 6.13.0-rc5-build2+ #1223 Tainted: G E -------------------------------- inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage. swapper/1/0 [HC0[0]:SC1[1]:HE1:SE0] takes: ffff88810babe228 (&rxnet->peer_hash_lock){+.?.}-{3:3}, at: rxrpc_put_peer+0xcb/0x180 {SOFTIRQ-ON-W} state was registered at: mark_usage+0x164/0x180 __lock_acquire+0x544/0x990 lock_acquire.part.0+0x103/0x280 _raw_spin_lock+0x2f/0x40 rxrpc_peer_keepalive_worker+0x144/0x440 process_one_work+0x486/0x7c0 process_scheduled_works+0x73/0x90 worker_thread+0x1c8/0x2a0 kthread+0x19b/0x1b0 ret_from_fork+0x24/0x40 ret_from_fork_asm+0x1a/0x30 irq event stamp: 972402 hardirqs last enabled at (972402): [] _raw_spin_unlock_irqrestore+0x2e/0x50 hardirqs last disabled at (972401): [] _raw_spin_lock_irqsave+0x18/0x60 softirqs last enabled at (972300): [] handle_softirqs+0x3ee/0x430 softirqs last disabled at (972313): [] __irq_exit_rcu+0x44/0x110

other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&rxnet->peer_hash_lock); lock(&rxnet->peer_hash_lock);

* DEADLOCK * 1 lock held by swapper/1/0: #0: ffffffff83576be0 (rcu_callback){....}-{0:0}, at: rcu_lock_acquire+0x7/0x30

stack backtrace: CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Tainted: G E 6.13.0-rc5-build2+ #1223 Tainted: [E]=UNSIGNED_MODULE Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014 Call Trace: dump_stack_lvl+0x57/0x80 print_usage_bug.part.0+0x227/0x240 valid_state+0x53/0x70 mark_lock_irq+0xa5/0x2f0 mark_lock+0xf7/0x170 mark_usage+0xe1/0x180 __lock_acquire+0x544/0x990 lock_acquire.part.0+0x103/0x280 _raw_spin_lock+0x2f/0x40 rxrpc_put_peer+0xcb/0x180 afs_free_addrlist+0x46/0x90 [kafs] rcu_do_batch+0x2d2/0x640 rcu_core+0x2f7/0x350 handle_softirqs+0x1ee/0x430 __irq_exit_rcu+0x44/0x110 irq_exit_rcu+0xa/0x30 sysvec_apic_timer_interrupt+0x7f/0xa0

CVSS v3
5.5
EG Score
5.5MEDIUMmedium confidence
EG Risk
25
EG Risk 25/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity55% × 45%
Impact severity (EG Severity): CVSS 5.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.3% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.3%
EPSS %ILE
24th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (5.5): severity, escalated by confirmed exploitation. This CVE's 5.5 is its impact severity (EG Severity), not escalated.

EG Severity
5.5 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.3% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-25). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

February 27, 2025

Last Modified

August 5, 2026

Advisory Details (3)

Auto-updated Jul 30, 2026
Patch available.
Web page

rxrpc, afs: Fix peer hash locking vs RCU callback - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/79d458c13056559d49b5e41fbc4b6890e68cf65b
Web page

rxrpc, afs: Fix peer hash locking vs RCU callback - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/10ba5a3d57af20e494e0d979d1894260989235dd
Web page

rxrpc, afs: Fix peer hash locking vs RCU callback - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/0e77dd41689637ac4e1b8fe0f27541f373640855

Patch Availability(13)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntulinux-virtual-hwe-24.04-edge (6.11.0-26.26) @ oracular2026-10-24ubuntu
ubuntulinux-virtual-6.8 (6.8.0-64.67) @ noble2026-10-24ubuntu
ubuntulinux-tools-realtime-6.8.1 (6.8.1-1025.26) @ noble2026-10-24ubuntu
ubuntulinux-virtual-hwe-22.04-edge (6.8.0-64.67~22.04.1) @ jammy2026-10-24ubuntu
ubuntulinux-tools-aws (6.11.0-1014.15) @ oracular2026-10-24ubuntu
ubuntulinux-tools-oracle-lts-24.04 (6.8.0-1029.30) @ noble2026-10-24ubuntu
ubuntulinux-tools-oracle-64k (6.11.0-1016.17) @ oracular2026-10-24ubuntu
ubuntulinux-tools-lowlatency-hwe-20.04-edge (6.8.0-64.67.1) @ noble2026-10-24ubuntu
ubuntulinux-tools-gcp-lts-24.04 (6.8.0-1033.35) @ noble2026-10-24ubuntu
ubuntulinux-tools-raspi-realtime-6.8 (6.8.0-2026.27) @ noble2026-10-24ubuntu
ubuntulinux-tools-raspi-6.8 (6.8.0-1031.35) @ noble2026-10-24ubuntu
ubuntulinux-tools-azure-nvidia-lts-24.04 (6.8.0-1022.23) @ noble2026-10-24ubuntu
linuxKernel @ 6.12.13 (fixes >=6.8.0)—osv

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(2 across 2 ecosystems)
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
linux—
  • every version up to 6.12.13-1: fixed in 6.12.13-1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
linux—
  • every version up to 6.12.13-1: fixed in 6.12.13-1
—

Weakness Classification(1)

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

All Vendor Advisories

(12)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 7× in last 7d / 38× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 96 of 197 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 4 repeat rows among the latest 100 are merged into the row they repeat. The 101 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-02 16:42 UTCEPSS rescoreEPSS 0.3% · 24th percentile
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  9. 2026-10-25 16:43 UTCEG score recompute
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  12. 2026-10-24 01:14 UTCEG score recompute
  13. 2026-10-24 01:14 UTCVendor advisory
  14. 2026-10-24 01:14 UTCGHSA enrichmentGHSA-4fj4-ghwr-gjf7 · GitHub CVSS 5.5
  15. 2026-10-23 16:30 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
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  19. 2026-10-19 23:25 UTCOSV refresh
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  21. 2026-10-18 05:46 UTCEG score recompute
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  1. 2026-10-13 16:32 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  2. 2026-10-12 17:19 UTCEG score recompute
  3. 2026-10-12 16:32 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  4. 2026-10-11 20:51 UTCEG score recompute
  5. 2026-10-11 19:01 UTCEG score recompute
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  7. 2026-10-11 13:47 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
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  19. 2026-09-27 03:45 UTCOSV refresh
  20. 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.3% · 21st percentile
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  37. 2026-09-07 13:18 UTCOSV refresh
  38. 2026-09-06 13:46 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
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  66. 2026-08-05 14:02 UTCEG score recompute
  67. 2026-08-05 14:02 UTCVendor advisory
  68. 2026-08-05 14:02 UTCGHSA enrichmentGHSA-4fj4-ghwr-gjf7 · GitHub CVSS 5.5
  69. 2026-08-04 15:09 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
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Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2025-21809?
CVE-2025-21809 is a medium-severity vulnerability; its CVE record was published on February 27, 2025. In the Linux kernel, the following vulnerability has been resolved: rxrpc, afs: Fix peer hash locking vs RCU callback In its address list, afs now retains pointers to and refs on one or more rxrpc_peer objects. The address list is freed under RCU and at this time, it puts the refs on those peers.…
When was the CVE record for CVE-2025-21809 published?
The CVE record for CVE-2025-21809 was published on February 27, 2025. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of August 5, 2026; the record at its source may have been updated since.
Is CVE-2025-21809 actively exploited?
CVE-2025-21809 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (24th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2025-21809?
CVE-2025-21809 has a CVSS v3 base score of 5.5 (NVD).
How do I remediate CVE-2025-21809?
A fix for CVE-2025-21809 is available: update to the fixed version the vendor names in its advisory.

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