Linux Kernel up to 7.2.2 IPv6 Segment Routing __ip_options_echo out-of-bounds

CVSS Meta Temp Score
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CTI Interest Score
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9.5$0-$5k0.00

Summaryinfo

A vulnerability categorized as very critical has been discovered in Linux Kernel up to 7.2.2. Affected is the function __ip_options_echo of the component IPv6 Segment Routing. Executing a manipulation can lead to out-of-bounds. This vulnerability is registered as CVE-2026-80840. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability classified as very critical was found in Linux Kernel up to 7.2.2. This vulnerability affects the function __ip_options_echo of the component IPv6 Segment Routing. The manipulation with an unknown input leads to a out-of-bounds vulnerability. The CWE definition for the vulnerability is CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: ipv6: seg6: clear IPv4 control block on IPIP decapsulation End.DX4 and End.DT4 decapsulate an IPv4 packet through decap_and_validate() and send it directly to IPv4 routing. The inner packet therefore bypasses ip_rcv_core(), which normally clears IPCB before IPv4 interprets skb->cb. The skb instead retains IP6CB data from the outer packet. IP6CB and IPCB use the same skb->cb storage, so IP6CB(skb)->lastopt overlaps IPCB(skb)->opt.optlen and srr, while IP6CB(skb)->nhoff overlaps rr and ts. The sender can make the stale optlen byte nonzero with a valid outer extension-header chain. The reproducers put an eight-byte Destination Options header immediately after the 40-byte IPv6 header and before the Segment Routing Header. ipv6_destopt_rcv() records the sender-controlled Destination Options offset in both lastopt and nhoff, setting them to 40. On the reproduced little-endian x86-64 kernel, IPv4 therefore sees optlen = 40 and rr = 40. Both tcp_v4_save_options() and __ip_options_echo() skip option copying when optlen is zero. Here optlen is 40, so the TCP SYN path allocates room for 40 bytes of option data and calls __ip_options_echo(). The stale rr value makes that function read inner packet byte 41 as the Record Route option length. The reproducers set that sender-controlled byte to 255, so __ip_options_echo() copies 255 bytes into the 40-byte option-data area. Separate End.DX4 and End.DT4 reproducers on the unpatched v7.2-rc5 kernel both produced: BUG: KASAN: slab-out-of-bounds in __ip_options_echo() Write of size 255 The relevant End.DX4 call path is: __ip_options_echo tcp_v4_route_req tcp_conn_request tcp_v4_conn_request tcp_rcv_state_process tcp_v4_do_rcv tcp_v4_rcv ip_protocol_deliver_rcu ip_local_deliver_finish ip_local_deliver input_action_end_dx4_finish input_action_end_dx4 The relevant End.DT4 call path is: __ip_options_echo tcp_v4_route_req tcp_conn_request tcp_v4_conn_request tcp_rcv_state_process tcp_v4_do_rcv tcp_v4_rcv ip_protocol_deliver_rcu ip_local_deliver_finish ip_local_deliver input_action_end_dt4 tcp_v4_save_options() is inlined into the tcp_v4_route_req() path, so it does not appear as a separate frame. When decap_and_validate() handles IPPROTO_IPIP, save the ingress interface from IP6CB, clear IPCB, and restore the saved value. Doing this in the common decapsulation path covers End.DX4, End.DT4, and End.DT46's IPv4 arm. Use IP6CB(skb)->iif rather than skb->skb_iif. These actions run after l3mdev processing, which can replace skb_iif with the L3 master; IP6CB iif still records the receiving interface set at IPv6 ingress.

The advisory is shared for download at git.kernel.org. This vulnerability was named CVE-2026-80840 since 08/26/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 09/04/2026).

Upgrading to version 5.10.269, 5.15.220, 6.1.187, 6.6.156, 6.12.108, 6.18.49, 7.1.13, 7.2.3 or 7.3-rc1 eliminates this vulnerability. Applying the patch 10fd1a8f58ac619a9e251f2858e2e2c8fd6cd667/eb0f422487228e140f3d609b032ac61aedcab8fa/9039e4f3e1c0ffe2b575b655b3f58fdd10f7e40c/f52f1e75716d2ee49e013edf204ac92337c72fd8/0e3f01fe2e704e76af4385b8a1742641885a191c/3e4476e58343fb8f2fffced9e22d935376b17aaf/bf1c1151560d11036a144d917fa4c131831342d7/f4be3b391265e24c7720fc867c50062b436acf33/44930446dde45a7a90fe1446fa38eb0e2c561646 is able to eliminate this problem.

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Productinfo

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Version

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 10.0
VulDB Meta Temp Score: 9.5

VulDB Base Score: 10.0
VulDB Temp Score: 9.5
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Out-of-bounds
CWE: CWE-125 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 5.10.269/5.15.220/6.1.187/6.6.156/6.12.108/6.18.49/7.1.13/7.2.3/7.3-rc1
Patch: 10fd1a8f58ac619a9e251f2858e2e2c8fd6cd667/eb0f422487228e140f3d609b032ac61aedcab8fa/9039e4f3e1c0ffe2b575b655b3f58fdd10f7e40c/f52f1e75716d2ee49e013edf204ac92337c72fd8/0e3f01fe2e704e76af4385b8a1742641885a191c/3e4476e58343fb8f2fffced9e22d935376b17aaf/bf1c1151560d11036a144d917fa4c131831342d7/f4be3b391265e24c7720fc867c50062b436acf33/44930446dde45a7a90fe1446fa38eb0e2c561646

Timelineinfo

08/26/2026 CVE reserved
09/04/2026 +9 days Advisory disclosed
09/04/2026 +0 days VulDB entry created
09/04/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-80840 (🔒)
GCVE (CVE): GCVE-0-2026-80840
GCVE (VulDB): GCVE-100-398980

Entryinfo

Created: 09/04/2026 18:41
Changes: 09/04/2026 18:41 (59)
Complete: 🔍
Cache ID: 216::103

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