Bluetooth: L2CAP: Fix ERTM re-init and zero pdu_len infinite loop

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Summary

CVECVE-2026-31498
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-22 14:16:48 UTC
Updated2026-04-28 14:41:39 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: Fix ERTM re-init and zero pdu_len infinite loop l2cap_config_req() processes CONFIG_REQ for channels in BT_CONNECTED state to support L2CAP reconfiguration (e.g. MTU changes). However, since both CONF_INPUT_DONE and CONF_OUTPUT_DONE are already set from the initial configuration, the reconfiguration path falls through to l2cap_ertm_init(), which re-initializes tx_q, srej_q, srej_list, and retrans_list without freeing the previous allocations and sets chan->sdu to NULL without freeing the existing skb. This leaks all previously allocated ERTM resources. Additionally, l2cap_parse_conf_req() does not validate the minimum value of remote_mps derived from the RFC max_pdu_size option. A zero value propagates to l2cap_segment_sdu() where pdu_len becomes zero, causing the while loop to never terminate since len is never decremented, exhausting all available memory. Fix the double-init by skipping l2cap_ertm_init() and l2cap_chan_ready() when the channel is already in BT_CONNECTED state, while still allowing the reconfiguration parameters to be updated through l2cap_parse_conf_req(). Also add a pdu_len zero check in l2cap_segment_sdu() as a safeguard.

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.000240000 probability, percentile 0.067930000 (date 2026-04-26)

Problem Types: CWE-835

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 96298f640104e4cd9a913a6e50b0b981829b94ff 9760b83cfd24b38caee663f429011a0dd6064fa9 git Not specified
CNA Linux Linux affected 96298f640104e4cd9a913a6e50b0b981829b94ff de37e2655b7abc3f59254c6b72256840f39fc6d5 git Not specified
CNA Linux Linux affected 96298f640104e4cd9a913a6e50b0b981829b94ff e7aab23b7df89a3d754a5f0a7d2237548b328bd0 git Not specified
CNA Linux Linux affected 96298f640104e4cd9a913a6e50b0b981829b94ff 52667c859fe33f70c2e711cb81bbd505d5eb8e75 git Not specified
CNA Linux Linux affected 96298f640104e4cd9a913a6e50b0b981829b94ff 9a21a631ee034b1573dce14b572a24943dbfd7ae git Not specified
CNA Linux Linux affected 96298f640104e4cd9a913a6e50b0b981829b94ff 900e4db5385ec2cacd372345a80ab9c8e105b3a3 git Not specified
CNA Linux Linux affected 96298f640104e4cd9a913a6e50b0b981829b94ff 042e2cd4bb11e5313b19b87593616524949e4c52 git Not specified
CNA Linux Linux affected 96298f640104e4cd9a913a6e50b0b981829b94ff 25f420a0d4cfd61d3d23ec4b9c56d9f443d91377 git Not specified
CNA Linux Linux affected 4ad03ff6f680681c5f78254e37c4c856fa953629 git Not specified
CNA Linux Linux affected b7d0ca715c1008acd2fc018f02a56fed88f78b75 git Not specified
CNA Linux Linux affected 799263eb37a4f7f6d39334046929c3bc92452a7f git Not specified
CNA Linux Linux affected 8828622fb9b4201eeb0870587052e3d834cfaf61 git Not specified
CNA Linux Linux affected b432ea85ab8472763870dd0f2c186130dd36d68c git Not specified
CNA Linux Linux affected 5.7 Not specified
CNA Linux Linux unaffected 5.7 semver Not specified
CNA Linux Linux unaffected 5.10.253 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.203 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.168 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.131 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.80 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.21 6.18.* semver Not specified
CNA Linux Linux unaffected 6.19.11 6.19.* semver Not specified
CNA Linux Linux unaffected 7.0 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/25f420a0d4cfd61d3d23ec4b9c56d9f443d91377 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/900e4db5385ec2cacd372345a80ab9c8e105b3a3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/de37e2655b7abc3f59254c6b72256840f39fc6d5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/9760b83cfd24b38caee663f429011a0dd6064fa9 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/042e2cd4bb11e5313b19b87593616524949e4c52 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/9a21a631ee034b1573dce14b572a24943dbfd7ae 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/e7aab23b7df89a3d754a5f0a7d2237548b328bd0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/52667c859fe33f70c2e711cb81bbd505d5eb8e75 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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