CVE-2025-38734 (GCVE-0-2025-38734)
Vulnerability from cvelistv5 – Published: 2025-09-05 17:20 – Updated: 2026-08-05 12:04
VLAI
EPSS
VEX
Title
net/smc: fix UAF on smcsk after smc_listen_out()
Summary
In the Linux kernel, the following vulnerability has been resolved:
net/smc: fix UAF on smcsk after smc_listen_out()
BPF CI testing report a UAF issue:
[ 16.446633] BUG: kernel NULL pointer dereference, address: 000000000000003 0
[ 16.447134] #PF: supervisor read access in kernel mod e
[ 16.447516] #PF: error_code(0x0000) - not-present pag e
[ 16.447878] PGD 0 P4D 0
[ 16.448063] Oops: Oops: 0000 [#1] PREEMPT SMP NOPT I
[ 16.448409] CPU: 0 UID: 0 PID: 9 Comm: kworker/0:1 Tainted: G OE 6.13.0-rc3-g89e8a75fda73-dirty #4 2
[ 16.449124] Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODUL E
[ 16.449502] Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/201 4
[ 16.450201] Workqueue: smc_hs_wq smc_listen_wor k
[ 16.450531] RIP: 0010:smc_listen_work+0xc02/0x159 0
[ 16.452158] RSP: 0018:ffffb5ab40053d98 EFLAGS: 0001024 6
[ 16.452526] RAX: 0000000000000001 RBX: 0000000000000002 RCX: 000000000000030 0
[ 16.452994] RDX: 0000000000000280 RSI: 00003513840053f0 RDI: 000000000000000 0
[ 16.453492] RBP: ffffa097808e3800 R08: ffffa09782dba1e0 R09: 000000000000000 5
[ 16.453987] R10: 0000000000000000 R11: 0000000000000000 R12: ffffa0978274640 0
[ 16.454497] R13: 0000000000000000 R14: 0000000000000000 R15: ffffa09782d4092 0
[ 16.454996] FS: 0000000000000000(0000) GS:ffffa097bbc00000(0000) knlGS:000000000000000 0
[ 16.455557] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003 3
[ 16.455961] CR2: 0000000000000030 CR3: 0000000102788004 CR4: 0000000000770ef 0
[ 16.456459] PKRU: 5555555 4
[ 16.456654] Call Trace :
[ 16.456832] <TASK >
[ 16.456989] ? __die+0x23/0x7 0
[ 16.457215] ? page_fault_oops+0x180/0x4c 0
[ 16.457508] ? __lock_acquire+0x3e6/0x249 0
[ 16.457801] ? exc_page_fault+0x68/0x20 0
[ 16.458080] ? asm_exc_page_fault+0x26/0x3 0
[ 16.458389] ? smc_listen_work+0xc02/0x159 0
[ 16.458689] ? smc_listen_work+0xc02/0x159 0
[ 16.458987] ? lock_is_held_type+0x8f/0x10 0
[ 16.459284] process_one_work+0x1ea/0x6d 0
[ 16.459570] worker_thread+0x1c3/0x38 0
[ 16.459839] ? __pfx_worker_thread+0x10/0x1 0
[ 16.460144] kthread+0xe0/0x11 0
[ 16.460372] ? __pfx_kthread+0x10/0x1 0
[ 16.460640] ret_from_fork+0x31/0x5 0
[ 16.460896] ? __pfx_kthread+0x10/0x1 0
[ 16.461166] ret_from_fork_asm+0x1a/0x3 0
[ 16.461453] </TASK >
[ 16.461616] Modules linked in: bpf_testmod(OE) [last unloaded: bpf_testmod(OE) ]
[ 16.462134] CR2: 000000000000003 0
[ 16.462380] ---[ end trace 0000000000000000 ]---
[ 16.462710] RIP: 0010:smc_listen_work+0xc02/0x1590
The direct cause of this issue is that after smc_listen_out_connected(),
newclcsock->sk may be NULL since it will releases the smcsk. Therefore,
if the application closes the socket immediately after accept,
newclcsock->sk can be NULL. A possible execution order could be as
follows:
smc_listen_work | userspace
-----------------------------------------------------------------
lock_sock(sk) |
smc_listen_out_connected() |
| \- smc_listen_out |
| | \- release_sock |
| |- sk->sk_data_ready() |
| fd = accept();
| close(fd);
| \- socket->sk = NULL;
/* newclcsock->sk is NULL now */
SMC_STAT_SERV_SUCC_INC(sock_net(newclcsock->sk))
Since smc_listen_out_connected() will not fail, simply swapping the order
of the code can easily fix this issue.
Severity
9.8 (Critical)
Assigner
References
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
3b2dec2603d5b06ad3af71c1164ca0b92df3d2a8 , < 070b4af44c4b6e4c35fb1ca7001a6a88fd2d318f
(git)
Affected: 3b2dec2603d5b06ad3af71c1164ca0b92df3d2a8 , < 2e765ba0ee0eae35688b443e97108308a716773e (git) Affected: 3b2dec2603d5b06ad3af71c1164ca0b92df3d2a8 , < 85545f1525f9fa9bf44fec77ba011024f15da342 (git) Affected: 3b2dec2603d5b06ad3af71c1164ca0b92df3d2a8 , < d9cef55ed49117bd63695446fb84b4b91815c0b4 (git) |
guessed | |
| Linux | Linux |
Affected:
4.18
Unaffected: 0 , < 4.18 (semver) Unaffected: 6.6.103 , ≤ 6.6.* (semver) Unaffected: 6.12.44 , ≤ 6.12.* (semver) Unaffected: 6.16.4 , ≤ 6.16.* (semver) Unaffected: 6.17 , ≤ * (original_commit_for_fix) |
guessed |
{
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{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/smc: fix UAF on smcsk after smc_listen_out()\n\nBPF CI testing report a UAF issue:\n\n [ 16.446633] BUG: kernel NULL pointer dereference, address: 000000000000003 0\n [ 16.447134] #PF: supervisor read access in kernel mod e\n [ 16.447516] #PF: error_code(0x0000) - not-present pag e\n [ 16.447878] PGD 0 P4D 0\n [ 16.448063] Oops: Oops: 0000 [#1] PREEMPT SMP NOPT I\n [ 16.448409] CPU: 0 UID: 0 PID: 9 Comm: kworker/0:1 Tainted: G OE 6.13.0-rc3-g89e8a75fda73-dirty #4 2\n [ 16.449124] Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODUL E\n [ 16.449502] Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/201 4\n [ 16.450201] Workqueue: smc_hs_wq smc_listen_wor k\n [ 16.450531] RIP: 0010:smc_listen_work+0xc02/0x159 0\n [ 16.452158] RSP: 0018:ffffb5ab40053d98 EFLAGS: 0001024 6\n [ 16.452526] RAX: 0000000000000001 RBX: 0000000000000002 RCX: 000000000000030 0\n [ 16.452994] RDX: 0000000000000280 RSI: 00003513840053f0 RDI: 000000000000000 0\n [ 16.453492] RBP: ffffa097808e3800 R08: ffffa09782dba1e0 R09: 000000000000000 5\n [ 16.453987] R10: 0000000000000000 R11: 0000000000000000 R12: ffffa0978274640 0\n [ 16.454497] R13: 0000000000000000 R14: 0000000000000000 R15: ffffa09782d4092 0\n [ 16.454996] FS: 0000000000000000(0000) GS:ffffa097bbc00000(0000) knlGS:000000000000000 0\n [ 16.455557] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003 3\n [ 16.455961] CR2: 0000000000000030 CR3: 0000000102788004 CR4: 0000000000770ef 0\n [ 16.456459] PKRU: 5555555 4\n [ 16.456654] Call Trace :\n [ 16.456832] \u003cTASK \u003e\n [ 16.456989] ? __die+0x23/0x7 0\n [ 16.457215] ? page_fault_oops+0x180/0x4c 0\n [ 16.457508] ? __lock_acquire+0x3e6/0x249 0\n [ 16.457801] ? exc_page_fault+0x68/0x20 0\n [ 16.458080] ? asm_exc_page_fault+0x26/0x3 0\n [ 16.458389] ? smc_listen_work+0xc02/0x159 0\n [ 16.458689] ? smc_listen_work+0xc02/0x159 0\n [ 16.458987] ? lock_is_held_type+0x8f/0x10 0\n [ 16.459284] process_one_work+0x1ea/0x6d 0\n [ 16.459570] worker_thread+0x1c3/0x38 0\n [ 16.459839] ? __pfx_worker_thread+0x10/0x1 0\n [ 16.460144] kthread+0xe0/0x11 0\n [ 16.460372] ? __pfx_kthread+0x10/0x1 0\n [ 16.460640] ret_from_fork+0x31/0x5 0\n [ 16.460896] ? __pfx_kthread+0x10/0x1 0\n [ 16.461166] ret_from_fork_asm+0x1a/0x3 0\n [ 16.461453] \u003c/TASK \u003e\n [ 16.461616] Modules linked in: bpf_testmod(OE) [last unloaded: bpf_testmod(OE) ]\n [ 16.462134] CR2: 000000000000003 0\n [ 16.462380] ---[ end trace 0000000000000000 ]---\n [ 16.462710] RIP: 0010:smc_listen_work+0xc02/0x1590\n\nThe direct cause of this issue is that after smc_listen_out_connected(),\nnewclcsock-\u003esk may be NULL since it will releases the smcsk. Therefore,\nif the application closes the socket immediately after accept,\nnewclcsock-\u003esk can be NULL. A possible execution order could be as\nfollows:\n\nsmc_listen_work | userspace\n-----------------------------------------------------------------\nlock_sock(sk) |\nsmc_listen_out_connected() |\n| \\- smc_listen_out |\n| | \\- release_sock |\n | |- sk-\u003esk_data_ready() |\n | fd = accept();\n | close(fd);\n | \\- socket-\u003esk = NULL;\n/* newclcsock-\u003esk is NULL now */\nSMC_STAT_SERV_SUCC_INC(sock_net(newclcsock-\u003esk))\n\nSince smc_listen_out_connected() will not fail, simply swapping the order\nof the code can easily fix this issue."
}
],
"metrics": [
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"cvssV3_1": {
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:N - The vulnerable `smc_listen_work()` handler is scheduled and driven entirely by an inbound TCP connection carrying the SMC experimental option and the subsequent CLC handshake messages from a remote peer, making this a net/ stack bug reachable via received packets.\nAC:L - The attacker can open unlimited concurrent SMC connections and retry the race indefinitely, and in the loopback-ism/local-peer scenario controls both sides outright (the connect and the accept()+close()); the race was reproduced reliably enough to be caught by CI.\nPR:N - The SMC CLC handshake performs no authentication whatsoever \u2014 the connection is accepted and the vulnerable worker runs before any credential check, so an unauthenticated remote peer reaches the code.\nUI:N - No deliberate victim action is required; the server application\u0027s normal accept()/close() sequence is what races the worker, and the attacker triggers the handshake itself.\nS:U - The use-after-free and resulting corruption are confined to kernel memory within the same security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - This is a use-after-free read of a freed `struct socket`, and the stale value is dereferenced as a `struct sock *` and chased through `sk_net` \u2014 with the freed slab reclaimed under attacker influence this yields arbitrary kernel-memory reads.\nI:H - The pointer read from the freed object is used as the base for `this_cpu_inc()` in SMC_STAT_SERV_SUCC_INC, turning the UAF into an attacker-influenceable kernel write primitive suitable for heap grooming and control-flow hijacking.\nA:H - The bug reproducibly oopses the smc_hs_wq kworker with a supervisor page fault (confirmed in the commit\u0027s trace), and a remote attacker can trigger it repeatedly to panic or destabilize the system."
}
]
}
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"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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{
"url": "https://git.kernel.org/stable/c/d9cef55ed49117bd63695446fb84b4b91815c0b4"
}
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"title": "net/smc: fix UAF on smcsk after smc_listen_out()",
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"datePublished": "2025-09-05T17:20:34.126Z",
"dateReserved": "2025-04-16T04:51:24.034Z",
"dateUpdated": "2026-08-05T12:04:24.867Z",
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"date": "2026-09-29",
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"id": "msrc_CVE-2025-38734",
"initial_release_date": "2025-09-07T01:09:52.000Z",
"product_status:fixed": "1",
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"source": "Microsoft CSAF VEX",
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"title": "net/smc: fix UAF on smcsk after smc_listen_out()",
"url": "https://msrc.microsoft.com/csaf/vex/2025/msrc_cve-2025-38734.json",
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{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/smc: fix UAF on smcsk after smc_listen_out()\n\nBPF CI testing report a UAF issue:\n\n [ 16.446633] BUG: kernel NULL pointer dereference, address: 000000000000003 0\n [ 16.447134] #PF: supervisor read access in kernel mod e\n [ 16.447516] #PF: error_code(0x0000) - not-present pag e\n [ 16.447878] PGD 0 P4D 0\n [ 16.448063] Oops: Oops: 0000 [#1] PREEMPT SMP NOPT I\n [ 16.448409] CPU: 0 UID: 0 PID: 9 Comm: kworker/0:1 Tainted: G OE 6.13.0-rc3-g89e8a75fda73-dirty #4 2\n [ 16.449124] Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODUL E\n [ 16.449502] Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/201 4\n [ 16.450201] Workqueue: smc_hs_wq smc_listen_wor k\n [ 16.450531] RIP: 0010:smc_listen_work+0xc02/0x159 0\n [ 16.452158] RSP: 0018:ffffb5ab40053d98 EFLAGS: 0001024 6\n [ 16.452526] RAX: 0000000000000001 RBX: 0000000000000002 RCX: 000000000000030 0\n [ 16.452994] RDX: 0000000000000280 RSI: 00003513840053f0 RDI: 000000000000000 0\n [ 16.453492] RBP: ffffa097808e3800 R08: ffffa09782dba1e0 R09: 000000000000000 5\n [ 16.453987] R10: 0000000000000000 R11: 0000000000000000 R12: ffffa0978274640 0\n [ 16.454497] R13: 0000000000000000 R14: 0000000000000000 R15: ffffa09782d4092 0\n [ 16.454996] FS: 0000000000000000(0000) GS:ffffa097bbc00000(0000) knlGS:000000000000000 0\n [ 16.455557] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003 3\n [ 16.455961] CR2: 0000000000000030 CR3: 0000000102788004 CR4: 0000000000770ef 0\n [ 16.456459] PKRU: 5555555 4\n [ 16.456654] Call Trace :\n [ 16.456832] \u003cTASK \u003e\n [ 16.456989] ? __die+0x23/0x7 0\n [ 16.457215] ? page_fault_oops+0x180/0x4c 0\n [ 16.457508] ? __lock_acquire+0x3e6/0x249 0\n [ 16.457801] ? exc_page_fault+0x68/0x20 0\n [ 16.458080] ? asm_exc_page_fault+0x26/0x3 0\n [ 16.458389] ? smc_listen_work+0xc02/0x159 0\n [ 16.458689] ? smc_listen_work+0xc02/0x159 0\n [ 16.458987] ? lock_is_held_type+0x8f/0x10 0\n [ 16.459284] process_one_work+0x1ea/0x6d 0\n [ 16.459570] worker_thread+0x1c3/0x38 0\n [ 16.459839] ? __pfx_worker_thread+0x10/0x1 0\n [ 16.460144] kthread+0xe0/0x11 0\n [ 16.460372] ? __pfx_kthread+0x10/0x1 0\n [ 16.460640] ret_from_fork+0x31/0x5 0\n [ 16.460896] ? __pfx_kthread+0x10/0x1 0\n [ 16.461166] ret_from_fork_asm+0x1a/0x3 0\n [ 16.461453] \u003c/TASK \u003e\n [ 16.461616] Modules linked in: bpf_testmod(OE) [last unloaded: bpf_testmod(OE) ]\n [ 16.462134] CR2: 000000000000003 0\n [ 16.462380] ---[ end trace 0000000000000000 ]---\n [ 16.462710] RIP: 0010:smc_listen_work+0xc02/0x1590\n\nThe direct cause of this issue is that after smc_listen_out_connected(),\nnewclcsock-\u003esk may be NULL since it will releases the smcsk. Therefore,\nif the application closes the socket immediately after accept,\nnewclcsock-\u003esk can be NULL. A possible execution order could be as\nfollows:\n\nsmc_listen_work | userspace\n-----------------------------------------------------------------\nlock_sock(sk) |\nsmc_listen_out_connected() |\n| \\- smc_listen_out |\n| | \\- release_sock |\n | |- sk-\u003esk_data_ready() |\n | fd = accept();\n | close(fd);\n | \\- socket-\u003esk = NULL;\n/* newclcsock-\u003esk is NULL now */\nSMC_STAT_SERV_SUCC_INC(sock_net(newclcsock-\u003esk))\n\nSince smc_listen_out_connected() will not fail, simply swapping the order\nof the code can easily fix this issue."
}
],
"id": "CVE-2025-38734",
"lastModified": "2026-07-30T06:23:38.660",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"exploitabilityScore": 3.9,
"impactScore": 5.9,
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary"
},
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 7.8,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"exploitabilityScore": 1.8,
"impactScore": 5.9,
"source": "nvd@nist.gov",
"type": "Primary"
}
]
},
"published": "2025-09-05T18:15:42.677",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/070b4af44c4b6e4c35fb1ca7001a6a88fd2d318f"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/2e765ba0ee0eae35688b443e97108308a716773e"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/85545f1525f9fa9bf44fec77ba011024f15da342"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/d9cef55ed49117bd63695446fb84b4b91815c0b4"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Modified",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-416"
}
],
"source": "nvd@nist.gov",
"type": "Primary"
}
]
}
},
"redhat_vex": {
"aggregate_severity": "Moderate",
"current_release_date": "2026-07-30T09:03:03+00:00",
"cve": "CVE-2025-38734",
"id": "CVE-2025-38734",
"initial_release_date": "2025-09-05T00:00:00+00:00",
"product_status:known_not_affected": "274",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: net/smc: fix UAF on smcsk after smc_listen_out()",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-38734.json",
"version": "3"
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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