In the Linux kernel, the following vulnerability has been resolved:
batman-adv: bla: avoid CRC corruption due to parallel claim add
batadv_bla_add_claim() is used to add claims and modify the backbone of
claims for CLAIM frames from remote backbones and local packets. When it
handles a claim, it needs to either
* add the new claim's CRC to the backbone CRC
* remove the already existing claim's CRC from the old backbone and add it
to the new backbone
But when the "new" claim code was running in parallel to the "change
backbone" code, it can happen that the CRC was invalid because the
backbone_gw of the claim was changed twice in the "new" claim code path:
* CPU0 creates the claim for gateway A and publishes it in the claim
hash. The crc16 of the address has not yet been added to A's crc at
this point.
* CPU1 processes a claim frame of gateway B for the same client, finds
the just published claim, and performs the ownership change: it
switches the pointer to B, removes the crc16 from A's crc - which
never contained it - and adds it to B's crc.
* CPU0 continues behind the creation branch, unconditionally switches
the pointer back to A without compensating B's crc (its remove_crc
is false for the creation path), and finally adds the crc16 to A's
crc
The CRC is then wrong for both:
* claim belongs to A: but CRC is not part of backbone A's CRC
* claim doesn't belong to B: CRC is still part of backbone B's CRC
This wrong CRC is never recomputated from the stored claims. For local
backbone claims, this can also not recovered using syncs.
To avoid this, split the functionality in clear separate parts:
* new claim which always adds claim CRC to the backbone CRC (but never
changes the already set backbone_gw of the claim back)
* update of existing claim which automatically changes the backbone_gw
entry and only updates both backbone CRCs when there was an actual change
batman-adv: bla: avoid CRC corruption due to parallel claim add
batadv_bla_add_claim() is used to add claims and modify the backbone of
claims for CLAIM frames from remote backbones and local packets. When it
handles a claim, it needs to either
* add the new claim's CRC to the backbone CRC
* remove the already existing claim's CRC from the old backbone and add it
to the new backbone
But when the "new" claim code was running in parallel to the "change
backbone" code, it can happen that the CRC was invalid because the
backbone_gw of the claim was changed twice in the "new" claim code path:
* CPU0 creates the claim for gateway A and publishes it in the claim
hash. The crc16 of the address has not yet been added to A's crc at
this point.
* CPU1 processes a claim frame of gateway B for the same client, finds
the just published claim, and performs the ownership change: it
switches the pointer to B, removes the crc16 from A's crc - which
never contained it - and adds it to B's crc.
* CPU0 continues behind the creation branch, unconditionally switches
the pointer back to A without compensating B's crc (its remove_crc
is false for the creation path), and finally adds the crc16 to A's
crc
The CRC is then wrong for both:
* claim belongs to A: but CRC is not part of backbone A's CRC
* claim doesn't belong to B: CRC is still part of backbone B's CRC
This wrong CRC is never recomputated from the stored claims. For local
backbone claims, this can also not recovered using syncs.
To avoid this, split the functionality in clear separate parts:
* new claim which always adds claim CRC to the backbone CRC (but never
changes the already set backbone_gw of the claim back)
* update of existing claim which automatically changes the backbone_gw
entry and only updates both backbone CRCs when there was an actual change
Metrics
Affected Vendors & Products
Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Thu, 17 Sep 2026 16:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: batman-adv: bla: avoid CRC corruption due to parallel claim add batadv_bla_add_claim() is used to add claims and modify the backbone of claims for CLAIM frames from remote backbones and local packets. When it handles a claim, it needs to either * add the new claim's CRC to the backbone CRC * remove the already existing claim's CRC from the old backbone and add it to the new backbone But when the "new" claim code was running in parallel to the "change backbone" code, it can happen that the CRC was invalid because the backbone_gw of the claim was changed twice in the "new" claim code path: * CPU0 creates the claim for gateway A and publishes it in the claim hash. The crc16 of the address has not yet been added to A's crc at this point. * CPU1 processes a claim frame of gateway B for the same client, finds the just published claim, and performs the ownership change: it switches the pointer to B, removes the crc16 from A's crc - which never contained it - and adds it to B's crc. * CPU0 continues behind the creation branch, unconditionally switches the pointer back to A without compensating B's crc (its remove_crc is false for the creation path), and finally adds the crc16 to A's crc The CRC is then wrong for both: * claim belongs to A: but CRC is not part of backbone A's CRC * claim doesn't belong to B: CRC is still part of backbone B's CRC This wrong CRC is never recomputated from the stored claims. For local backbone claims, this can also not recovered using syncs. To avoid this, split the functionality in clear separate parts: * new claim which always adds claim CRC to the backbone CRC (but never changes the already set backbone_gw of the claim back) * update of existing claim which automatically changes the backbone_gw entry and only updates both backbone CRCs when there was an actual change | |
| Title | batman-adv: bla: avoid CRC corruption due to parallel claim add | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
|
Projects
Sign in to view the affected projects.
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-17T16:12:23.742Z
Reserved: 2026-09-17T16:02:15.092Z
Link: CVE-2026-93203
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-17T17:18:16.627
Modified: 2026-09-17T17:18:16.627
Link: CVE-2026-93203
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.