CVE-2026-45842 [Medium] | Security Vulnerability in Linux Kernel

In the Linux kernel, the following vulnerability has been resolved: slip: reject VJ receive packets on instances with no rstate array slhc_init() accepts rslots == 0 as a valid configuration, with the documented meaning of 'no receive compression'. In that case the allocation loop in slhc_init() is skipped, so comp->rstate stays NULL and comp->rslot_limit stays 0 (from the kzalloc of struct slcompress). The receive helpers do not defend against that configuration. slhc_uncompress() dereferences comp->rstate[x] when the VJ header carries an explicit connection ID, and slhc_remember() later assigns cs = &comp->rstate[...] after only comparing the packet's slot number to comp->rslot_limit. Because rslot_limit is 0, slot 0 passes the range check, and the code dereferences a NULL rstate. The configuration is reachable in-tree through PPP. PPPIOCSMAXCID stores its argument in a signed int, and (val >> 16) uses arithmetic shift. Passing 0xffff0000 therefore sign-extends to -1, so val2 + 1 is 0 and ppp_generic.c ends up calling slhc_init(0, 1). Because /dev/ppp open is gated by ns_capable(CAP_NET_ADMIN), the whole path is reachable from an unprivileged user namespace. Once the malformed VJ state is installed, any inbound VJ-compressed or VJ-uncompressed frame that selects slot 0 crashes the kernel in softirq context: Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: 0010:slhc_uncompress (drivers/net/slip/slhc.c:519) Call Trace: <TASK> ppp_receive_nonmp_frame (drivers/net/ppp/ppp_generic.c:2466) ppp_input (drivers/net/ppp/ppp_generic.c:2359) ppp_async_process (drivers/net/ppp/ppp_async.c:492) tasklet_action_common (kernel/softirq.c:926) handle_softirqs (kernel/softirq.c:623) run_ksoftirqd (kernel/softirq.c:1055) smpboot_thread_fn (kernel/smpboot.c:160) kthread (kernel/kthread.c:436) ret_from_fork (arch/x86/kernel/process.c:164) </TASK> Reject the receive side on such instances instead of touching rstate. slhc_uncompress() falls through to its existing 'bad' label, which bumps sls_i_error and enters the toss state. slhc_remember() mirrors that with an explicit sls_i_error increment followed by slhc_toss(); the sls_i_runt counter is not used here because a missing rstate is an internal configuration state, not a runt packet. The transmit path is unaffected: the only in-tree caller that picks rslots from userspace (ppp_generic.c) still supplies tslots >= 1, and slip.c always calls slhc_init(16, 16), so comp->tstate remains valid and slhc_compress() continues to work.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-27	0.16%	0.11%	-0.05%
2	2026-06-15	0.02%	0.16%	+0.15%
3	2026-05-27	—	0.02%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-27

0.16%

0.11%

-0.05%

2026-06-15

0.02%

0.16%

+0.15%

2026-05-27

—

0.02%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
5.5	3.1	MEDIUM	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	1.8	3.6	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

5.5

3.1

MEDIUM

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

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

1.8

3.6

[email protected]

OS Trackers for CVE-2026-45842

vendor	priority	summary	link
`debian`	not yet assigned	CVE-2026-45842 not yet assigned priority: Debian including 2 source packages (linux, linux-6.1), 6 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 6.	https://security-tracker.debian.org/tracker/CVE-2026-45842
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2026-45842
`suse`	medium	—	https://www.suse.com/security/cve/CVE-2026-45842/
`ubuntu`	medium	CVE-2026-45842 medium priority: Ubuntu including 158 source packages (linux, linux-allwinner-5.19, …), 1422 status rows across 9 suites (bionic, focal, jammy, noble, questing, resolute, trusty, upstream, xenial): DNE 1024, ignored 173, needed 141, released 84.	https://ubuntu.com/security/CVE-2026-45842

Affected software / configurations for CVE-2026-45842

Vendor	Product	Version	Raw CPE
linux	linux_kernel	>= 2.6.32.70, < 2.6.33	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 3.2.75, < 3.3	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 3.4.111, < 3.5	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 3.10.96, < 3.11	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 3.12.53, < 3.13	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 3.14.60, < 3.15	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 3.18.27, < 3.19	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 4.1.17, < 4.2	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 4.3.5, < 5.10.258	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 5.11, < 5.15.209	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 5.16, < 6.1.175	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.2, < 6.6.141	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.7, < 6.12.91	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.13, < 6.18.33	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.19, < 7.0.10	cpe:2.3:o:linux:linux_kernel::::::::

References for CVE-2026-45842

URL	Tags
https://git.kernel.org/stable/c/3d71c961febddd855d3ae9a519eeb96c8023f430	Patch
https://git.kernel.org/stable/c/4aa9eca6fda2919027dfd7a7cc69334982d89586	Patch
https://git.kernel.org/stable/c/72304fec672e8aac9ee7b9c475db96b37cca8d8d	Patch
https://git.kernel.org/stable/c/7b0d9e878ec2b21d99ae8051b3dda59cdb66c152	Patch
https://git.kernel.org/stable/c/9e1ff0eead073c4f46d874ad2526b7dda5465faf	Patch
https://git.kernel.org/stable/c/c6980e8b1a86288167f34966fa5219031999b6f1	Patch
https://git.kernel.org/stable/c/de42f86e2cf5028a97e74c25869d1a962b13c301	Patch
https://git.kernel.org/stable/c/e76607442d5b73e1ba6768f501ef815bb58c2c0e	Patch

URL

CVE-2026-45842 | slip: reject VJ receive packets on instances with no rstate array

Exploit prediction scoring system (EPSS) score for CVE-2026-45842

Common vulnerability scoring system (CVSS) metrics for CVE-2026-45842

Weakness enumeration for CVE-2026-45842

GitHub Security Advisory for CVE-2026-45842

OS Trackers for CVE-2026-45842

Affected software / configurations for CVE-2026-45842

References for CVE-2026-45842