FKIE_CVE-2026-45842
Vulnerability from fkie_nvd - Published: 2026-05-27 11:16 - Updated: 2026-06-26 18:51
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved:
slip: reject VJ receive packets on instances with no rstate array
slhc_init() accepts rslots == 0 as a valid configuration, with the
documented meaning of 'no receive compression'. In that case the
allocation loop in slhc_init() is skipped, so comp->rstate stays
NULL and comp->rslot_limit stays 0 (from the kzalloc of struct
slcompress).
The receive helpers do not defend against that configuration.
slhc_uncompress() dereferences comp->rstate[x] when the VJ header
carries an explicit connection ID, and slhc_remember() later assigns
cs = &comp->rstate[...] after only comparing the packet's slot number
to comp->rslot_limit. Because rslot_limit is 0, slot 0 passes the
range check, and the code dereferences a NULL rstate.
The configuration is reachable in-tree through PPP. PPPIOCSMAXCID
stores its argument in a signed int, and (val >> 16) uses arithmetic
shift. Passing 0xffff0000 therefore sign-extends to -1, so val2 + 1
is 0 and ppp_generic.c ends up calling slhc_init(0, 1). Because
/dev/ppp open is gated by ns_capable(CAP_NET_ADMIN), the whole path
is reachable from an unprivileged user namespace. Once the malformed
VJ state is installed, any inbound VJ-compressed or VJ-uncompressed
frame that selects slot 0 crashes the kernel in softirq context:
Oops: general protection fault, probably for non-canonical
address 0xdffffc0000000000: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
RIP: 0010:slhc_uncompress (drivers/net/slip/slhc.c:519)
Call Trace:
<TASK>
ppp_receive_nonmp_frame (drivers/net/ppp/ppp_generic.c:2466)
ppp_input (drivers/net/ppp/ppp_generic.c:2359)
ppp_async_process (drivers/net/ppp/ppp_async.c:492)
tasklet_action_common (kernel/softirq.c:926)
handle_softirqs (kernel/softirq.c:623)
run_ksoftirqd (kernel/softirq.c:1055)
smpboot_thread_fn (kernel/smpboot.c:160)
kthread (kernel/kthread.c:436)
ret_from_fork (arch/x86/kernel/process.c:164)
</TASK>
Reject the receive side on such instances instead of touching rstate.
slhc_uncompress() falls through to its existing 'bad' label, which
bumps sls_i_error and enters the toss state. slhc_remember() mirrors
that with an explicit sls_i_error increment followed by slhc_toss();
the sls_i_runt counter is not used here because a missing rstate is
an internal configuration state, not a runt packet.
The transmit path is unaffected: the only in-tree caller that picks
rslots from userspace (ppp_generic.c) still supplies tslots >= 1, and
slip.c always calls slhc_init(16, 16), so comp->tstate remains valid
and slhc_compress() continues to work.
References
Impacted products
| Vendor | Product | Version | |
|---|---|---|---|
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * |
{
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{
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"product": "Linux",
"programFiles": [
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],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
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},
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"versionType": "git"
},
{
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"versionType": "git"
},
{
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"status": "affected",
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"versionType": "semver"
},
{
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"status": "affected",
"version": "3.2.75",
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},
{
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"status": "affected",
"version": "3.4.111",
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},
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},
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]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"drivers/net/slip/slhc.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
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},
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},
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"status": "unaffected",
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},
{
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"status": "unaffected",
"version": "6.1.175",
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},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
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},
{
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"status": "unaffected",
"version": "6.12.91",
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},
{
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"status": "unaffected",
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},
{
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"status": "unaffected",
"version": "7.0.10",
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},
{
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"status": "unaffected",
"version": "7.1",
"versionType": "original_commit_for_fix"
}
]
}
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"configurations": [
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"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nslip: reject VJ receive packets on instances with no rstate array\n\nslhc_init() accepts rslots == 0 as a valid configuration, with the\ndocumented meaning of \u0027no receive compression\u0027. In that case the\nallocation loop in slhc_init() is skipped, so comp-\u003erstate stays\nNULL and comp-\u003erslot_limit stays 0 (from the kzalloc of struct\nslcompress).\n\nThe receive helpers do not defend against that configuration.\nslhc_uncompress() dereferences comp-\u003erstate[x] when the VJ header\ncarries an explicit connection ID, and slhc_remember() later assigns\ncs = \u0026comp-\u003erstate[...] after only comparing the packet\u0027s slot number\nto comp-\u003erslot_limit. Because rslot_limit is 0, slot 0 passes the\nrange check, and the code dereferences a NULL rstate.\n\nThe configuration is reachable in-tree through PPP. PPPIOCSMAXCID\nstores its argument in a signed int, and (val \u003e\u003e 16) uses arithmetic\nshift. Passing 0xffff0000 therefore sign-extends to -1, so val2 + 1\nis 0 and ppp_generic.c ends up calling slhc_init(0, 1). Because\n/dev/ppp open is gated by ns_capable(CAP_NET_ADMIN), the whole path\nis reachable from an unprivileged user namespace. Once the malformed\nVJ state is installed, any inbound VJ-compressed or VJ-uncompressed\nframe that selects slot 0 crashes the kernel in softirq context:\n\n Oops: general protection fault, probably for non-canonical\n address 0xdffffc0000000000: 0000 [#1] SMP KASAN NOPTI\n KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]\n RIP: 0010:slhc_uncompress (drivers/net/slip/slhc.c:519)\n Call Trace:\n \u003cTASK\u003e\n ppp_receive_nonmp_frame (drivers/net/ppp/ppp_generic.c:2466)\n ppp_input (drivers/net/ppp/ppp_generic.c:2359)\n ppp_async_process (drivers/net/ppp/ppp_async.c:492)\n tasklet_action_common (kernel/softirq.c:926)\n handle_softirqs (kernel/softirq.c:623)\n run_ksoftirqd (kernel/softirq.c:1055)\n smpboot_thread_fn (kernel/smpboot.c:160)\n kthread (kernel/kthread.c:436)\n ret_from_fork (arch/x86/kernel/process.c:164)\n \u003c/TASK\u003e\n\nReject the receive side on such instances instead of touching rstate.\nslhc_uncompress() falls through to its existing \u0027bad\u0027 label, which\nbumps sls_i_error and enters the toss state. slhc_remember() mirrors\nthat with an explicit sls_i_error increment followed by slhc_toss();\nthe sls_i_runt counter is not used here because a missing rstate is\nan internal configuration state, not a runt packet.\n\nThe transmit path is unaffected: the only in-tree caller that picks\nrslots from userspace (ppp_generic.c) still supplies tslots \u003e= 1, and\nslip.c always calls slhc_init(16, 16), so comp-\u003etstate remains valid\nand slhc_compress() continues to work."
}
],
"id": "CVE-2026-45842",
"lastModified": "2026-06-26T18:51:05.930",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 5.5,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
"exploitabilityScore": 1.8,
"impactScore": 3.6,
"source": "nvd@nist.gov",
"type": "Primary"
}
]
},
"published": "2026-05-27T11:16:23.600",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/3d71c961febddd855d3ae9a519eeb96c8023f430"
},
{
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"url": "https://git.kernel.org/stable/c/4aa9eca6fda2919027dfd7a7cc69334982d89586"
},
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{
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},
{
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},
{
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"tags": [
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],
"url": "https://git.kernel.org/stable/c/c6980e8b1a86288167f34966fa5219031999b6f1"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
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],
"url": "https://git.kernel.org/stable/c/de42f86e2cf5028a97e74c25869d1a962b13c301"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
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],
"url": "https://git.kernel.org/stable/c/e76607442d5b73e1ba6768f501ef815bb58c2c0e"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Analyzed",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-476"
}
],
"source": "nvd@nist.gov",
"type": "Primary"
}
]
}
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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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