Description
In the Linux kernel, the following vulnerability has been resolved:
calipso: keep BIG TCP payload_len in calipso_skbuff_setattr()
calipso_skbuff_setattr() adjusts payload_len by the length of the
option it inserts or resizes:
payload = ntohs(ip6_hdr->payload_len);
ip6_hdr->payload_len = htons(payload + len_delta);
GRO can build BIG TCP packets larger than IPV6_MAXPLEN, and stores
payload_len == 0 for them; ipv6_payload_len() then falls back to
skb->len. For such a packet forwarded to a destination mapped to
CALIPSO, the code above writes len_delta (or 65536 + len_delta when
shrinking) into payload_len, and ipv6_payload_len() no longer falls
back to skb->len. nf_tables, conntrack and sch_cake rely on it.
The same arithmetic also wraps when a packet grows past IPV6_MAXPLEN,
and a BIG TCP packet that shrinks below IPV6_MAXPLEN should get its
real length back.
Set payload_len from the skb length with ipv6_set_payload_len(), which
stores 0 above IPV6_MAXPLEN and the real length otherwise, as
ipv6_gro_complete() does. The network header was just reset to
skb->data, so skb->len - sizeof(*ip6_hdr) is the payload length.
Tested on one kernel (arm64, QEMU) with SELinux permissive, a minimal
mdp-generated policy (network_peer_controls=1), "netlabelctl calipso
add pass doi:16" and a NetLabel mapping of fd00:2::/64 to CALIPSO
DOI 16. calipso_skbuff_setattr() was called through
netlbl_skbuff_setattr() from a test-only debugfs hook (not part of
this patch) adding a level-only label; payload_len after the call:
case before fix after fix real length
1000, unlabeled 1016 1016 1016
70000 GSO, payload_len 0 16 0 70016
65530 GSO, grows past MAXPLEN 10 0 65546
65540 GSO with a 24 byte hop
header, shrinks below MAXPLEN 65528 65532 65532
1000 with a 24 byte hop header 992 992 992
(0 means ipv6_payload_len() returns the real length.) On the forward
path, with a client injecting unlabeled UDP through a router to a
server, the router adds the CALIPSO option and the server delivers all
datagrams (Udp6InDatagrams 5, Ip6InTruncatedPkts 0) with this patch.
calipso: keep BIG TCP payload_len in calipso_skbuff_setattr()
calipso_skbuff_setattr() adjusts payload_len by the length of the
option it inserts or resizes:
payload = ntohs(ip6_hdr->payload_len);
ip6_hdr->payload_len = htons(payload + len_delta);
GRO can build BIG TCP packets larger than IPV6_MAXPLEN, and stores
payload_len == 0 for them; ipv6_payload_len() then falls back to
skb->len. For such a packet forwarded to a destination mapped to
CALIPSO, the code above writes len_delta (or 65536 + len_delta when
shrinking) into payload_len, and ipv6_payload_len() no longer falls
back to skb->len. nf_tables, conntrack and sch_cake rely on it.
The same arithmetic also wraps when a packet grows past IPV6_MAXPLEN,
and a BIG TCP packet that shrinks below IPV6_MAXPLEN should get its
real length back.
Set payload_len from the skb length with ipv6_set_payload_len(), which
stores 0 above IPV6_MAXPLEN and the real length otherwise, as
ipv6_gro_complete() does. The network header was just reset to
skb->data, so skb->len - sizeof(*ip6_hdr) is the payload length.
Tested on one kernel (arm64, QEMU) with SELinux permissive, a minimal
mdp-generated policy (network_peer_controls=1), "netlabelctl calipso
add pass doi:16" and a NetLabel mapping of fd00:2::/64 to CALIPSO
DOI 16. calipso_skbuff_setattr() was called through
netlbl_skbuff_setattr() from a test-only debugfs hook (not part of
this patch) adding a level-only label; payload_len after the call:
case before fix after fix real length
1000, unlabeled 1016 1016 1016
70000 GSO, payload_len 0 16 0 70016
65530 GSO, grows past MAXPLEN 10 0 65546
65540 GSO with a 24 byte hop
header, shrinks below MAXPLEN 65528 65532 65532
1000 with a 24 byte hop header 992 992 992
(0 means ipv6_payload_len() returns the real length.) On the forward
path, with a client injecting unlabeled UDP through a router to a
server, the router adds the CALIPSO option and the server delivers all
datagrams (Udp6InDatagrams 5, Ip6InTruncatedPkts 0) with this patch.
Published:
2026-10-28
Score:
n/a
EPSS:
n/a
KEV:
No
Impact:
n/a
Action:
n/a
Analysis
No analysis available yet.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
||||||||||||||||||
| Linux | Linux | affected |
|
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No data.
No data available yet.
Remediation
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Tracking
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Advisories
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References
History
Wed, 28 Oct 2026 10:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: calipso: keep BIG TCP payload_len in calipso_skbuff_setattr() calipso_skbuff_setattr() adjusts payload_len by the length of the option it inserts or resizes: payload = ntohs(ip6_hdr->payload_len); ip6_hdr->payload_len = htons(payload + len_delta); GRO can build BIG TCP packets larger than IPV6_MAXPLEN, and stores payload_len == 0 for them; ipv6_payload_len() then falls back to skb->len. For such a packet forwarded to a destination mapped to CALIPSO, the code above writes len_delta (or 65536 + len_delta when shrinking) into payload_len, and ipv6_payload_len() no longer falls back to skb->len. nf_tables, conntrack and sch_cake rely on it. The same arithmetic also wraps when a packet grows past IPV6_MAXPLEN, and a BIG TCP packet that shrinks below IPV6_MAXPLEN should get its real length back. Set payload_len from the skb length with ipv6_set_payload_len(), which stores 0 above IPV6_MAXPLEN and the real length otherwise, as ipv6_gro_complete() does. The network header was just reset to skb->data, so skb->len - sizeof(*ip6_hdr) is the payload length. Tested on one kernel (arm64, QEMU) with SELinux permissive, a minimal mdp-generated policy (network_peer_controls=1), "netlabelctl calipso add pass doi:16" and a NetLabel mapping of fd00:2::/64 to CALIPSO DOI 16. calipso_skbuff_setattr() was called through netlbl_skbuff_setattr() from a test-only debugfs hook (not part of this patch) adding a level-only label; payload_len after the call: case before fix after fix real length 1000, unlabeled 1016 1016 1016 70000 GSO, payload_len 0 16 0 70016 65530 GSO, grows past MAXPLEN 10 0 65546 65540 GSO with a 24 byte hop header, shrinks below MAXPLEN 65528 65532 65532 1000 with a 24 byte hop header 992 992 992 (0 means ipv6_payload_len() returns the real length.) On the forward path, with a client injecting unlabeled UDP through a router to a server, the router adds the CALIPSO option and the server delivers all datagrams (Udp6InDatagrams 5, Ip6InTruncatedPkts 0) with this patch. | |
| Title | calipso: keep BIG TCP payload_len in calipso_skbuff_setattr() | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-10-28T10:35:47.854Z
Reserved: 2026-09-25T10:25:14.400Z
Link: CVE-2026-99191
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-10-28T11:17:40.080
Modified: 2026-10-28T11:17:40.080
Link: CVE-2026-99191
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.