CVE-2025-39955

HIGHNVD 7.87.8—
EchelonGraph scoreMEDIUM confidence

Score 7.8 from GitHub Security Advisory (severity: HIGH) published 2025-10-09. NVD baseline CVSS 7.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
7.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.8Exploit: NoneExposed: 0

A fix is available — apply it.

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

tcp: Clear tcp_sk(sk)->fastopen_rsk in tcp_disconnect().

syzbot reported the splat below where a socket had tcp_sk(sk)->fastopen_rsk in the TCP_ESTABLISHED state. [0]

syzbot reused the server-side TCP Fast Open socket as a new client before the TFO socket completes 3WHS:

  • accept()
  • connect(AF_UNSPEC)
  • connect() to another destination

As of accept(), sk->sk_state is TCP_SYN_RECV, and tcp_disconnect() changes it to TCP_CLOSE and makes connect() possible, which restarts timers.

Since tcp_disconnect() forgot to clear tcp_sk(sk)->fastopen_rsk, the retransmit timer triggered the warning and the intended packet was not retransmitted.

Let's call reqsk_fastopen_remove() in tcp_disconnect().

[0]: WARNING: CPU: 2 PID: 0 at net/ipv4/tcp_timer.c:542 tcp_retransmit_timer (net/ipv4/tcp_timer.c:542 (discriminator 7)) Modules linked in: CPU: 2 UID: 0 PID: 0 Comm: swapper/2 Not tainted 6.17.0-rc5-g201825fb4278 #62 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:tcp_retransmit_timer (net/ipv4/tcp_timer.c:542 (discriminator 7)) Code: 41 55 41 54 55 53 48 8b af b8 08 00 00 48 89 fb 48 85 ed 0f 84 55 01 00 00 0f b6 47 12 3c 03 74 0c 0f b6 47 12 3c 04 74 04 90 <0f> 0b 90 48 8b 85 c0 00 00 00 48 89 ef 48 8b 40 30 e8 6a 4f 06 3e RSP: 0018:ffffc900002f8d40 EFLAGS: 00010293 RAX: 0000000000000002 RBX: ffff888106911400 RCX: 0000000000000017 RDX: 0000000002517619 RSI: ffffffff83764080 RDI: ffff888106911400 RBP: ffff888106d5c000 R08: 0000000000000001 R09: ffffc900002f8de8 R10: 00000000000000c2 R11: ffffc900002f8ff8 R12: ffff888106911540 R13: ffff888106911480 R14: ffff888106911840 R15: ffffc900002f8de0 FS: 0000000000000000(0000) GS:ffff88907b768000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f8044d69d90 CR3: 0000000002c30003 CR4: 0000000000370ef0 Call Trace: tcp_write_timer (net/ipv4/tcp_timer.c:738) call_timer_fn (kernel/time/timer.c:1747) __run_timers (kernel/time/timer.c:1799 kernel/time/timer.c:2372) timer_expire_remote (kernel/time/timer.c:2385 kernel/time/timer.c:2376 kernel/time/timer.c:2135) tmigr_handle_remote_up (kernel/time/timer_migration.c:944 kernel/time/timer_migration.c:1035) __walk_groups.isra.0 (kernel/time/timer_migration.c:533 (discriminator 1)) tmigr_handle_remote (kernel/time/timer_migration.c:1096) handle_softirqs (./arch/x86/include/asm/jump_label.h:36 ./include/trace/events/irq.h:142 kernel/softirq.c:580) irq_exit_rcu (kernel/softirq.c:614 kernel/softirq.c:453 kernel/softirq.c:680 kernel/softirq.c:696) sysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1050 (discriminator 35) arch/x86/kernel/apic/apic.c:1050 (discriminator 35))

CVSS v3
7.8
EG Score
7.8(medium)
EG Risk
35(Track)
EG Risk 35/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity78% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
4.4%
KEV
Not listed

Published

October 9, 2025

Last Modified

July 14, 2026

Advisory Details (9)

Auto-updated Jul 14, 2026
No patch confirmed yet.
generic

SSA-019113

https://cert-portal.siemens.com/productcert/html/ssa-019113.html
generic

tcp: Clear tcp_sk(sk)->fastopen_rsk in tcp_disconnect(). - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/fa4749c065644af4db496b338452a69a3e5147d9
generic

tcp: Clear tcp_sk(sk)->fastopen_rsk in tcp_disconnect(). - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/dfd06131107e7b699ef1e2a24ed2f7d17c917753
generic

tcp: Clear tcp_sk(sk)->fastopen_rsk in tcp_disconnect(). - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/ae313d14b45eca7a6bb29cb9bf396d977e7d28fb
generic

tcp: Clear tcp_sk(sk)->fastopen_rsk in tcp_disconnect(). - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/a4378dedd6e07e62f2fccb17d78c9665718763d0
generic

tcp: Clear tcp_sk(sk)->fastopen_rsk in tcp_disconnect(). - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/7ec092a91ff351dcde89c23e795b73a328274db6
generic

tcp: Clear tcp_sk(sk)->fastopen_rsk in tcp_disconnect(). - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/45c8a6cc2bcd780e634a6ba8e46bffbdf1fc5c01
generic

tcp: Clear tcp_sk(sk)->fastopen_rsk in tcp_disconnect(). - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/33a4fdf0b4a25f8ce65380c3b0136b407ca57609
generic

tcp: Clear tcp_sk(sk)->fastopen_rsk in tcp_disconnect(). - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/17d699727577814198d744d6afe54735c6b54c99

Vendor Advisories for CVE-2025-39955(12)

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

Patch Availability(30)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulinux-tools-azure-edge (6.8.0-1051.57~22.04.1) @ jammy2026-05-29ubuntu
ubuntulinux-tools-raspi-nolpae (5.15.0.1097.95) @ jammy2026-05-29ubuntu
ubuntulinux-tools-azure-edge (5.15.0.1110.119~20.04.1) @ focal2026-05-29ubuntu
ubuntulinux-tools-raspi-realtime-6.8 (6.8.0-2040.41) @ noble2026-05-29ubuntu
ubuntulinux-tools-azure-fips-6.8 (6.8.0-1052.58+fips1) @ noble2026-05-29ubuntu
ubuntulinux-tools-azure-lts-22.04 (5.15.0.1109.107) @ jammy2026-05-29ubuntu
ubuntulinux-tools-azure-fips-5.15 (5.15.0.1109.94) @ jammy2026-05-29ubuntu
ubuntulinux-xilinx-zynqmp (6.8.0.1029.30) @ noble2026-05-29ubuntu
ubuntulinux-tools-aws-edge (5.15.0.1100.107~20.04.1) @ focal2026-05-29ubuntu
ubuntulinux-tools-nvidia-tegra-rt-5.15 (5.15.0.1052.52) @ jammy2026-05-29ubuntu
ubuntulinux-tools-nvidia-tegra-igx-rt-5.15 (5.15.0.1041.43) @ jammy2026-05-29ubuntu
ubuntulinux-tools-gcp-fips-5.15 (5.15.0.1100.90) @ jammy2026-05-29ubuntu
ubuntulinux-tools-realtime-5.15 (5.15.0.1099.103) @ jammy2026-05-29ubuntu
redhatkernel-rt-0:3.10.0-1160.144.1.rt56.1296.el72025-12-22redhat
redhatkernel-0:3.10.0-1160.144.1.el72025-12-22redhat
redhatkernel-0:5.14.0-427.103.1.el9_42025-12-17redhat
redhatkernel-rt-0:5.14.0-284.150.1.rt14.435.el9_22025-12-17redhat
redhatkernel-0:5.14.0-70.158.1.el9_02025-12-17redhat
redhatkernel-0:4.18.0-372.173.1.el8_62025-12-17redhat
redhatkernel-0:4.18.0-477.123.1.el8_82025-12-17redhat
redhatkernel-0:5.14.0-284.150.1.el9_22025-12-17redhat
redhatkernel-0:4.18.0-305.182.1.el8_42025-12-17redhat
redhatkernel-rt-0:5.14.0-70.158.1.rt21.230.el9_02025-12-17redhat
redhatkernel-0:4.18.0-193.178.1.el8_22025-12-17redhat
redhatkernel-0:6.12.0-55.47.1.el10_02025-12-02redhat
redhatkernel-0:5.14.0-570.69.1.el9_62025-12-01redhat
redhatkernel-0:4.18.0-553.87.1.el8_102025-12-01redhat
redhatkernel-0:5.14.0-611.11.1.el9_72025-12-01redhat
redhatkernel-rt-0:4.18.0-553.87.1.rt7.428.el8_102025-12-01redhat
redhatkernel-0:6.12.0-124.13.1.el10_12025-11-24redhat

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.

Additional Vendor Advisories

(14)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 10× in last 7d / 46× 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. 2026-07-23 02:55 UTCEG score recompute
  2. 2026-07-22 14:07 UTCEPSS rescore
  3. 2026-07-22 14:07 UTCEPSS rescore
  4. 2026-07-21 15:24 UTCEPSS rescore
  5. 2026-07-20 17:07 UTCEPSS rescore
  6. 2026-07-19 14:30 UTCEPSS rescore
  7. 2026-07-19 14:30 UTCEPSS rescore
  8. 2026-07-18 10:04 UTCEPSS rescore
  9. 2026-07-18 10:04 UTCEPSS rescore
  10. 2026-07-16 17:02 UTCEPSS rescore
  11. 2026-07-15 16:57 UTCEPSS rescore
  12. 2026-07-15 16:57 UTCEPSS rescore
  13. 2026-07-15 01:59 UTCEPSS rescore
  14. 2026-07-15 01:59 UTCEPSS rescore
  15. 2026-07-14 13:19 UTCNVD updateCVSS v3 → 7.8 · severity → HIGH
  16. 2026-07-13 06:12 UTCEPSS rescore
  17. 2026-07-12 05:46 UTCEPSS rescore
  18. 2026-07-11 08:27 UTCEPSS rescore
  19. 2026-07-11 08:27 UTCEPSS rescore
  20. 2026-07-09 19:09 UTCEPSS rescore
  21. 2026-07-09 19:09 UTCEPSS rescore
  22. 2026-07-07 13:45 UTCEPSS rescore
  23. 2026-07-06 16:27 UTCEPSS rescore
  24. 2026-07-06 16:27 UTCEPSS rescore
  25. 2026-07-06 12:41 UTCOSV refresh
Show 61 more
  1. 2026-07-06 02:23 UTCEPSS rescore
  2. 2026-07-05 02:30 UTCEPSS rescore
  3. 2026-07-04 06:30 UTCEPSS rescore
  4. 2026-07-01 15:06 UTCEPSS rescore
  5. 2026-07-01 15:06 UTCEPSS rescore
  6. 2026-06-30 23:22 UTCEPSS rescore
  7. 2026-06-30 23:22 UTCEPSS rescore
  8. 2026-06-29 14:06 UTCEPSS rescore
  9. 2026-06-29 14:06 UTCEPSS rescore
  10. 2026-06-28 14:07 UTCEPSS rescore
  11. 2026-06-28 14:07 UTCEPSS rescore
  12. 2026-06-28 04:55 UTCEPSS rescore
  13. 2026-06-28 04:55 UTCEPSS rescore
  14. 2026-06-27 03:08 UTCEPSS rescore
  15. 2026-06-27 03:08 UTCEPSS rescore
  16. 2026-06-25 13:49 UTCEPSS rescore
  17. 2026-06-25 13:49 UTCEPSS rescore
  18. 2026-06-24 14:04 UTCEPSS rescore
  19. 2026-06-24 14:04 UTCEPSS rescore
  20. 2026-06-23 21:32 UTCEPSS rescore
  21. 2026-06-23 21:32 UTCEPSS rescore
  22. 2026-06-22 14:25 UTCEPSS rescore
  23. 2026-06-22 14:25 UTCEPSS rescore
  24. 2026-06-21 14:56 UTCEPSS rescore
  25. 2026-06-21 14:56 UTCEPSS rescore
  26. 2026-06-21 01:59 UTCEPSS rescore
  27. 2026-06-21 01:59 UTCEPSS rescore
  28. 2026-06-19 19:25 UTCEPSS rescore
  29. 2026-06-19 19:25 UTCEPSS rescore
  30. 2026-06-18 00:35 UTCOSV refresh
  31. 2026-06-17 17:52 UTCEPSS rescore
  32. 2026-06-16 17:52 UTCEPSS rescore
  33. 2026-06-16 17:52 UTCEPSS rescore
  34. 2026-06-14 23:18 UTCMITRE cvelistV5
  35. 2026-06-14 23:17 UTCEPSS rescore
  36. 2026-06-13 23:00 UTCEPSS rescore
  37. 2026-06-12 23:11 UTCEPSS rescore
  38. 2026-06-11 14:00 UTCEPSS rescore
  39. 2026-06-10 22:18 UTCEPSS rescore
  40. 2026-06-10 13:22 UTCEPSS rescore
  41. 2026-06-08 14:16 UTCEPSS rescore
  42. 2026-06-08 14:16 UTCEPSS rescore
  43. 2026-06-07 15:24 UTCEPSS rescore
  44. 2026-06-06 13:47 UTCEPSS rescore
  45. 2026-06-06 13:47 UTCEPSS rescore
  46. 2026-06-05 22:46 UTCEPSS rescore
  47. 2026-06-05 22:46 UTCEPSS rescore
  48. 2026-06-05 06:10 UTCEPSS rescore
  49. 2026-06-05 06:10 UTCEPSS rescore
  50. 2026-06-04 13:12 UTCEPSS rescore
  51. 2026-06-04 13:12 UTCEPSS rescore
  52. 2026-06-02 20:12 UTCEPSS rescore
  53. 2026-06-01 13:51 UTCEPSS rescore
  54. 2026-06-01 13:51 UTCEPSS rescore
  55. 2026-05-31 22:30 UTCEPSS rescore
  56. 2026-05-31 22:30 UTCEPSS rescore
  57. 2026-05-31 00:16 UTCEPSS rescore
  58. 2026-05-29 21:11 UTCEG score recompute
  59. 2026-05-29 21:11 UTCVendor advisory
  60. 2026-05-29 21:10 UTCGHSA enrichment
  61. 2026-05-29 13:44 UTCEPSS rescore

Related CVEs(same vendor)

Frequently asked(5)

What is CVE-2025-39955?
CVE-2025-39955 is a high vulnerability published on October 9, 2025. In the Linux kernel, the following vulnerability has been resolved: tcp: Clear tcpsk(sk)->fastopenrsk in tcp_disconnect(). syzbot reported the splat below where a socket had tcpsk(sk)->fastopenrsk in the TCP_ESTABLISHED state. [0] syzbot reused the server-side TCP Fast Open socket as a new client…
When was CVE-2025-39955 disclosed?
CVE-2025-39955 was first published in the National Vulnerability Database on October 9, 2025, with the most recent update on July 14, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2025-39955 actively exploited?
CVE-2025-39955 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 4.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2025-39955?
CVE-2025-39955 has a CVSS v3 base score of 7.8 (NVD).
How do I remediate CVE-2025-39955?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2025-39955, 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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