CVE-2026-74577 (GCVE-0-2026-74577)
Vulnerability from cvelistv5
Published
2026-08-15 12:28
Modified
2026-08-19 16:39
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
net: mpls: initialize rtm_tos in mpls_getroute()
mpls_getroute() builds the RTM_NEWROUTE reply to an RTM_GETROUTE
request by filling a struct rtmsg allocated from an skb whose data
area is not zeroed (alloc_skb(NLMSG_GOODSIZE, ...)). It sets every
field of the header except rtm_tos:
r = nlmsg_data(nlh);
r->rtm_family = AF_MPLS;
r->rtm_dst_len = 20;
r->rtm_src_len = 0;
r->rtm_table = RT_TABLE_MAIN;
r->rtm_type = RTN_UNICAST;
r->rtm_scope = RT_SCOPE_UNIVERSE;
r->rtm_protocol = rt->rt_protocol;
r->rtm_flags = 0;
struct rtmsg has no padding, so the one uninitialised byte rtm_tos
(offset 3) is copied straight to user space on recvmsg(), leaking a
byte of uninitialised heap memory. This is in contrast to
mpls_dump_route(), which fills the very same header and does set
rtm_tos = 0.
Initialize rtm_tos to 0, matching mpls_dump_route().
Reproduced with KMSAN by adding an MPLS route and issuing a
non-RTM_F_FIB_MATCH RTM_GETROUTE for its label:
BUG: KMSAN: kernel-infoleak in _copy_to_iter+0x36c/0x33f0
_copy_to_iter+0x36c/0x33f0
__skb_datagram_iter+0x196/0x12c0
skb_copy_datagram_iter+0x5b/0x210
netlink_recvmsg+0x37b/0xef0
...
Uninit was created at:
__alloc_skb+0x8ca/0x10e0
mpls_getroute+0x1280/0x3a40
rtnetlink_rcv_msg+0x1138/0x15a0
...
Byte 19 of 64 is uninitialized
(byte 19 = nlmsghdr(16) + rtmsg offset 3 = rtm_tos)
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 397fc9e5cefee0c33b86811fbddb0decb7288c52 Version: 397fc9e5cefee0c33b86811fbddb0decb7288c52 Version: 397fc9e5cefee0c33b86811fbddb0decb7288c52 Version: 397fc9e5cefee0c33b86811fbddb0decb7288c52 Version: 397fc9e5cefee0c33b86811fbddb0decb7288c52 Version: 397fc9e5cefee0c33b86811fbddb0decb7288c52 Version: 397fc9e5cefee0c33b86811fbddb0decb7288c52 Version: 397fc9e5cefee0c33b86811fbddb0decb7288c52 |
||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/mpls/af_mpls.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
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"status": "affected",
"version": "397fc9e5cefee0c33b86811fbddb0decb7288c52",
"versionType": "git"
},
{
"lessThan": "466b474a8deb0c93b5280c6d261e5eda6482eca7",
"status": "affected",
"version": "397fc9e5cefee0c33b86811fbddb0decb7288c52",
"versionType": "git"
},
{
"lessThan": "ba56f88aab18d982f2a21f11390f4d8a8897782a",
"status": "affected",
"version": "397fc9e5cefee0c33b86811fbddb0decb7288c52",
"versionType": "git"
},
{
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"status": "affected",
"version": "397fc9e5cefee0c33b86811fbddb0decb7288c52",
"versionType": "git"
},
{
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"status": "affected",
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"versionType": "git"
},
{
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"versionType": "git"
},
{
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"status": "affected",
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"versionType": "git"
},
{
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"status": "affected",
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"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"net/mpls/af_mpls.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "4.13"
},
{
"lessThan": "4.13",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.265",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.216",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.183",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.151",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.103",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.44",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.8",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.10.265",
"versionStartIncluding": "4.13",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.15.216",
"versionStartIncluding": "4.13",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.1.183",
"versionStartIncluding": "4.13",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.151",
"versionStartIncluding": "4.13",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.103",
"versionStartIncluding": "4.13",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.44",
"versionStartIncluding": "4.13",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.1.8",
"versionStartIncluding": "4.13",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.2",
"versionStartIncluding": "4.13",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: mpls: initialize rtm_tos in mpls_getroute()\n\nmpls_getroute() builds the RTM_NEWROUTE reply to an RTM_GETROUTE\nrequest by filling a struct rtmsg allocated from an skb whose data\narea is not zeroed (alloc_skb(NLMSG_GOODSIZE, ...)). It sets every\nfield of the header except rtm_tos:\n\n\tr = nlmsg_data(nlh);\n\tr-\u003ertm_family\t = AF_MPLS;\n\tr-\u003ertm_dst_len\t= 20;\n\tr-\u003ertm_src_len\t= 0;\n\tr-\u003ertm_table\t= RT_TABLE_MAIN;\n\tr-\u003ertm_type\t= RTN_UNICAST;\n\tr-\u003ertm_scope\t= RT_SCOPE_UNIVERSE;\n\tr-\u003ertm_protocol = rt-\u003ert_protocol;\n\tr-\u003ertm_flags\t= 0;\n\nstruct rtmsg has no padding, so the one uninitialised byte rtm_tos\n(offset 3) is copied straight to user space on recvmsg(), leaking a\nbyte of uninitialised heap memory. This is in contrast to\nmpls_dump_route(), which fills the very same header and does set\nrtm_tos = 0.\n\nInitialize rtm_tos to 0, matching mpls_dump_route().\n\nReproduced with KMSAN by adding an MPLS route and issuing a\nnon-RTM_F_FIB_MATCH RTM_GETROUTE for its label:\n\n BUG: KMSAN: kernel-infoleak in _copy_to_iter+0x36c/0x33f0\n _copy_to_iter+0x36c/0x33f0\n __skb_datagram_iter+0x196/0x12c0\n skb_copy_datagram_iter+0x5b/0x210\n netlink_recvmsg+0x37b/0xef0\n ...\n Uninit was created at:\n __alloc_skb+0x8ca/0x10e0\n mpls_getroute+0x1280/0x3a40\n rtnetlink_rcv_msg+0x1138/0x15a0\n ...\n Byte 19 of 64 is uninitialized\n\n(byte 19 = nlmsghdr(16) + rtmsg offset 3 = rtm_tos)"
}
],
"providerMetadata": {
"dateUpdated": "2026-08-19T16:39:14.107Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/248718fd88b146d8bdc7610ecd1eb4cd16e0b5a1"
},
{
"url": "https://git.kernel.org/stable/c/466b474a8deb0c93b5280c6d261e5eda6482eca7"
},
{
"url": "https://git.kernel.org/stable/c/ba56f88aab18d982f2a21f11390f4d8a8897782a"
},
{
"url": "https://git.kernel.org/stable/c/95651461cf77cc6590fa08c87667717e5dcfa55d"
},
{
"url": "https://git.kernel.org/stable/c/1fea5ff0eb4aa7e951bb3d380248566c473aa377"
},
{
"url": "https://git.kernel.org/stable/c/a5cdd2407dd890f741f59b8367e4c6c101cce154"
},
{
"url": "https://git.kernel.org/stable/c/2dc2fffc704a4365cae1aae078ba62223aaeff93"
},
{
"url": "https://git.kernel.org/stable/c/295dd295e2137e10e9a5b1891d97e0f08de76f03"
}
],
"title": "net: mpls: initialize rtm_tos in mpls_getroute()",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-74577",
"datePublished": "2026-08-15T12:28:14.408Z",
"dateReserved": "2026-08-15T05:44:03.917Z",
"dateUpdated": "2026-08-19T16:39:14.107Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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