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CVE-2026-89783
xfrm6: fix out-of-bounds write in xfrm6_input_addr() when secpath is full
Published 2026-09-16 (33 days ago) by the Linux kernel CNA. Subsystem net/ipv6. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-89783 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4841-1 · 2026-10-17 · text | 6.1.190-1 | Update the kernel and reboot. DLA-4841-1 shipped the fix on 2026-10-17, in 6.1.190-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
The depth check in xfrm6_input_addr() is off by one: if (1 + sp->len == XFRM_MAX_DEPTH) goto drop; ... sp->xvec[sp->len++] = x; xfrm_input() can leave sp->len == XFRM_MAX_DEPTH, and the transport-mode receive path re-enters IPv6 input via xfrm_trans_reinject() with that secpath preserved. If the inner packet carries a destination-options HAO option or a type-2 routing header, xfrm6_input_addr() is called with sp->len == XFRM_MAX_DEPTH; the check (1 + 6 == 6) is false, so sp->xvec[sp->len++] writes one slot past the 6-element xvec[]. The write stays within the sec_path allocation (invisible to KASAN); UBSAN_BOUNDS flags it and panics under panic_on_warn. Use "sp->len >= XFRM_MAX_DEPTH", matching xfrm_input(). This also restores one chain level the old check rejected at sp->len == 5. UBSAN: array-index-out-of-bounds in net/ipv6/xfrm6_input.c:309:10 index 6 is out of range for type 'xfrm_state *[6]'
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
net/ipv6/xfrm6_input.c
- What this is
- NETWORKING [IPSEC]MAINTAINERS section matched on net/ipv6/xfrm* · netdev@vger.kernel.org · Maintained
Check it on the machine
grep -wE 'CONFIG_IPV6|CONFIG_XFRM' /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
Show whether Debian builds this, per release
Debian builds this code. Every release below compiles the affected file into the kernels it ships.
- bookworm, trixie, forky, sid, bookworm · linux-6.12y
- y
- built into the kernel image on every flavour - only a patch removes it
- Build switches
- CONFIG_IPV6, CONFIG_XFRM
- Reads as
- all on means the file is compiled; any one off means it is not.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-09-16 (33 days ago)source
- CVSS
- 9.8 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.71%, higher than 52.8% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/ipv6
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.25 | 5.10.270 | 91fc387f63c0 |
| 2.6.25 | 5.15.221 | 68e8737fe8e7 |
| 2.6.25 | 6.1.188 | 8fe2c53fb81f |
| 2.6.25 | 6.6.157 | bdcda866c89f |
| 2.6.25 | 6.12.110 | 48996649222e |
| 2.6.25 | 6.18.52 | 0f679e0523dd |
| 2.6.25 | 7.2.6 | 5f35a29a5eed |
| 2.6.25 | 7.3 | 5d9e3bf34fec |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4841-1 | 2026-10-17 | bookworm 6.1.190-1 | tracker |
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:NAttack vector, network
- The bug is on the IPv6 receive path: remote ESP/AH packets are processed by xfrm_input() until the secpath is full, then xfrm_trans_reinject() re-enters ip6_rcv_finish so an inner destopt HAO or type-2 routing header reaches xfrm6_input_addr() on internet-facing IPsec/MIP6 VPN and home-agent endpoints.
- AC:LAttack complexity, low
- Once a max-depth transport-mode IPsec bundle and a MIP6 destopt or routing state are present, a peer sending nested IPsec then an inner HAO or type-2 RH deterministically bypasses the off-by-one check (1+6!=6) and writes xvec[6]; no race or attacker-uncontrollable layout is required.
- PR:NPrivileges required, none
- No local account or capability on the victim is required. A remote IPsec/MIP6 peer triggers the overflow with packets accepted by already-installed SAs; creating those SAs is a deployment precondition rather than attacker privilege on the host.
- UI:NUser interaction, none
- Packets are processed in NAPI/softirq and the deferred xfrm_trans_reinject workqueue with no victim action such as mounting a filesystem, opening a file, or otherwise interacting with the host.
- S:UScope, unchanged
- The out-of-bounds write corrupts the skb sec_path in the host kernel that processed the packet; this is standard kernel memory corruption, not a VM escape, IOMMU bypass, or other cross-authority boundary.
- C:HConfidentiality impact, high
- The overflow writes a kernel xfrm_state pointer past xvec[] into the adjacent xfrm_offload object and sets len to 7, so later xvec walks and teardown treat that overlapping memory as a state pointer, giving a memory-corruption disclosure primitive.
- I:HIntegrity impact, high
- This is an out-of-bounds write of a kernel pointer one slot past the 6-element xvec[] into ovec, which per kernel CVSS guidance is high integrity impact and can be shaped toward control-flow hijacking.
- A:HAvailability impact, high
- UBSAN_BOUNDS flags the overflow and panics under panic_on_warn, and the corrupted sec_path (len=7 overlapping ovec) can oops during later xvec iteration or skb_ext teardown, fully denying availability.