VulnerabilityPublished 6 May 2026Updated 7 Sep 2026

CVE-2026-43194: Linux kernel · net: consume xmit errors of GSO frames

Affects Linux kernelSource GCVE Database

Authoritative record:CVE-2026-43194· High 7.5

Not known to be exploited · CVSS 7.5 High · fixed in 6.8.0-1060.63~22.04.1 : patch Linux kernel soon.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.5% chance of exploitation in 30 days – higher than 44% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 6.8.0-1060.63~22.04.1, 6.8.0-1063.69~22.04.1, 6.8.0-1060.61~22.04.1 +24

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

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

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 6 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
Ubuntu 26.04 LTSlinux-azure-fde`pkg:deb/ubuntu/linux-azure-fde@7.0.0-1008.8?arch=source&distro=resolute`Other threats	Affected 7.0.0-1003.3 – 7.0.0-1008.8 4 affected builds	Fixed in–
Ubuntu 25.10linux`pkg:deb/ubuntu/linux@6.17.0-40.40?arch=source&distro=questing`Other threats	Affected 6.14.0-15.15 – 6.17.0-40.40 20 affected builds	Fixed in–
Ubuntu 25.10linux-aws`pkg:deb/ubuntu/linux-aws@6.17.0-1019.19?arch=source&distro=questing`Other threats	Affected 6.14.0-1005.5 – 6.17.0-1019.19 17 affected builds	Fixed in–
Ubuntu 25.10linux-azure`pkg:deb/ubuntu/linux-azure@6.17.0-1020.20?arch=source&distro=questing`Other threats	Affected 6.14.0-1004.4 – 6.17.0-1020.20 16 affected builds	Fixed in–
Ubuntu 25.10linux-azure-fde`pkg:deb/ubuntu/linux-azure-fde@6.17.0-1017.17?arch=source&distro=questing`Other threats	Affected 6.17.0-1003.3 – 6.17.0-1017.17 10 affected builds	Fixed in–
Ubuntu 25.10linux-gcp`pkg:deb/ubuntu/linux-gcp@6.17.0-1020.22?arch=source&distro=questing`Other threats	Affected 6.14.0-1006.6 – 6.17.0-1020.22 17 affected builds	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

In the Linux kernel, the following vulnerability has been resolved: net: consume xmit errors of GSO frames udpgro_frglist.sh and udpgro_bench.sh are the flakiest tests currently in NIPA. They fail in the same exact way, TCP GRO test stalls occasionally and the test gets killed after 10min. These tests use veth to simulate GRO. They attach a trivial ("return XDP_PASS;") XDP program to the veth to force TSO off and NAPI on. Digging into the failure mode we can see that the connection is completely stuck after a burst of drops. The sender's snd_nxt is at sequence number N [1], but the receiver claims to have received (rcv_nxt) up to N + 3 * MSS [2]. Last piece of the puzzle is that senders rtx queue is not empty (let's say the block in the rtx queue is at sequence number N - 4 * MSS [3]). In this state, sender sends a retransmission from the rtx queue with a single segment, and sequence numbers N-4*MSS:N-3*MSS [3]. Receiver sees it and responds with an ACK all the way up to N + 3 * MSS [2]. But sender will reject this ack as TCP_ACK_UNSENT_DATA because it has no recollection of ever sending data that far out [1]. And we are stuck. The root cause is the mess of the xmit return codes. veth returns an error when it can't xmit a frame. We end up with a loss event like this: ------------------------------------------------- | GSO super frame 1 | GSO super frame 2 | |-----------------------------------------------| | seg | seg | seg | seg | seg | seg | seg | seg | | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | ------------------------------------------------- x ok ok <ok>| ok ok ok <x> \\ snd_nxt "x" means packet lost by veth, and "ok" means it went thru. Since veth has TSO disabled in this test it sees individual segments. Segment 1 is on the retransmit queue and will be resent. So why did the sender not advance snd_nxt even tho it clearly did send up to seg 8? tcp_write_xmit() interprets the return code from the core to mean that data has not been sent at all. Since TCP deals with GSO super frames, not individual segment the crux of the problem is that loss of a single segment can be interpreted as loss of all. TCP only sees the last return code for the last segment of the GSO frame (in <> brackets in the diagram above). Of course for the problem to occur we need a setup or a device without a Qdisc. Otherwise Qdisc layer disconnects the protocol layer from the device errors completely. We have multiple ways to fix this. 1) make veth not return an error when it lost a packet. While this is what I think we did in the past, the issue keeps reappearing and it's annoying to debug. The game of whack a mole is not great. 2) fix the damn return codes We only talk about NETDEV_TX_OK and NETDEV_TX_BUSY in the documentation, so maybe we should make the return code from ndo_start_xmit() a boolean. I like that the most, but perhaps some ancient, not-really-networking protocol would suffer. 3) make TCP ignore the errors It is not entirely clear to me what benefit TCP gets from interpreting the result of ip_queue_xmit()? Specifically once the connection is established and we're pushing data - packet loss is just packet loss? 4) this fix Ignore the rc in the Qdisc-less+GSO case, since it's unreliable. We already always return OK in the TCQ_F_CAN_BYPASS case. In the Qdisc-less case let's be a bit more conservative and only mask the GSO errors. This path is taken by non-IP-"networks" like CAN, MCTP etc, so we could regress some ancient thing. This is the simplest, but also maybe the hackiest fix? Similar fix has been proposed by Eric in the past but never committed because original reporter was working with an OOT driver and wasn't providing feedback (see Link).

GCVE source: db.gcve.eu
OSV ID: UBUNTU-CVE-2026-43194
Osv Schema Version: 1.7.0
Ecosystems: Ubuntu:Pro:14.04:LTS, Ubuntu:Pro:16.04:LTS, Ubuntu:16.04:LTS, Ubuntu:Pro:FIPS:16.04:LTS, Ubuntu:Pro:18.04:LTS, Ubuntu:18.04:LTS, Ubuntu:Pro:FIPS-updates:18.04:LTS, Ubuntu:Pro:FIPS:18.04:LTS, Ubuntu:Pro:20.04:LTS, Ubuntu:20.04:LTS, Ubuntu:Pro:FIPS-updates:20.04:LTS, Ubuntu:Pro:FIPS:20.04:LTS, Ubuntu:22.04:LTS, Ubuntu:Nvidia-BlueField:22.04:LTS, Ubuntu:Pro:FIPS-preview:22.04:LTS, Ubuntu:Pro:FIPS-updates:22.04:LTS, Ubuntu:Pro:Realtime:22.04:LTS, Ubuntu:24.04:LTS, Ubuntu:Nvidia-BlueField:24.04:LTS, Ubuntu:Pro:FIPS-updates:24.04:LTS, Ubuntu:Pro:Realtime:24.04:LTS, Ubuntu:25.10, Ubuntu:26.04:LTS
CVSS version: 3.1

References

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