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CVE Record

CVE-2023-53726: arm64: csum: Fix OoB access in IP checksum code for negative lengths

In the Linux kernel, the following vulnerability has been resolved: arm64: csum: Fix OoB access in IP checksum code for negative lengths Although commit c2c24edb1d9c ("arm64: csum: Fix pathological zero-length calls") added an early return for zero-length input, syzkaller has popped up with an example of a _negative_ length which causes an undefined shift and an out-of-bounds read: | BUG: KASAN: slab-out-of-bounds in do_csum+0x44/0x254 arch/arm64/lib/csum.c:39 | Read of size 4294966928 at addr ffff0000d7ac0170 by task syz-executor412/5975 | | CPU: 0 PID: 5975 Comm: syz-executor412 Not tainted 6.4.0-rc4-syzkaller-g908f31f2a05b #0 | Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/25/2023 | Call trace: | dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:233 | show_stack+0x2c/0x44 arch/arm64/kernel/stacktrace.c:240 | __dump_stack lib/dump_stack.c:88 [inline] | dump_stack_lvl+0xd0/0x124 lib/dump_stack.c:106 | print_address_description mm/kasan/report.c:351 [inline] | print_report+0x174/0x514 mm/kasan/report.c:462 | kasan_report+0xd4/0x130 mm/kasan/report.c:572 | kasan_check_range+0x264/0x2a4 mm/kasan/generic.c:187 | __kasan_check_read+0x20/0x30 mm/kasan/shadow.c:31 | do_csum+0x44/0x254 arch/arm64/lib/csum.c:39 | csum_partial+0x30/0x58 lib/checksum.c:128 | gso_make_checksum include/linux/skbuff.h:4928 [inline] | __udp_gso_segment+0xaf4/0x1bc4 net/ipv4/udp_offload.c:332 | udp6_ufo_fragment+0x540/0xca0 net/ipv6/udp_offload.c:47 | ipv6_gso_segment+0x5cc/0x1760 net/ipv6/ip6_offload.c:119 | skb_mac_gso_segment+0x2b4/0x5b0 net/core/gro.c:141 | __skb_gso_segment+0x250/0x3d0 net/core/dev.c:3401 | skb_gso_segment include/linux/netdevice.h:4859 [inline] | validate_xmit_skb+0x364/0xdbc net/core/dev.c:3659 | validate_xmit_skb_list+0x94/0x130 net/core/dev.c:3709 | sch_direct_xmit+0xe8/0x548 net/sched/sch_generic.c:327 | __dev_xmit_skb net/core/dev.c:3805 [inline] | __dev_queue_xmit+0x147c/0x3318 net/core/dev.c:4210 | dev_queue_xmit include/linux/netdevice.h:3085 [inline] | packet_xmit+0x6c/0x318 net/packet/af_packet.c:276 | packet_snd net/packet/af_packet.c:3081 [inline] | packet_sendmsg+0x376c/0x4c98 net/packet/af_packet.c:3113 | sock_sendmsg_nosec net/socket.c:724 [inline] | sock_sendmsg net/socket.c:747 [inline] | __sys_sendto+0x3b4/0x538 net/socket.c:2144 Extend the early return to reject negative lengths as well, aligning our implementation with the generic code in lib/checksum.c

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue affects arm64 checksum handling. A malformed or inconsistent length can make checksum code read outside its intended memory range. The public record shows a syzkaller/KASAN finding and stable kernel fixes, but does not provide CVSS, confirmed real-world exploitation, or product-specific distro advisories.

Executive priority

Treat as a kernel maintenance item for arm64 fleets rather than an emergency based on current evidence. Prioritize patch confirmation where Linux networking is mission-critical, but do not assume active exploitation without new vendor or KEV evidence.

Technical view

The arm64 do_csum path only rejected zero-length input. A negative length could trigger an undefined shift and out-of-bounds read during checksum calculation, seen through UDP/IPv6 GSO and packet send paths. The fix extends the early return to reject negative lengths, matching generic checksum behavior.

Likely exposure

Exposure is most relevant to arm64 Linux systems running affected kernel versions or unfixed downstream builds. The source lists Linux as affected and provides stable commit fixes, but does not identify specific distributions, appliances, cloud images, or CPEs.

Exploitation context

The evidence shows syzkaller discovered the bug and KASAN reported an out-of-bounds read. The bundle marks KEV false and provides no cited evidence of active exploitation, public exploit use, privilege impact, or reliable remote attackability.

Researcher notes

The record is strong on root cause and fix direction, but weak on impact boundaries. Further analysis should focus on affected branch ranges, distro backports, reachability of the UDP/GSO paths, and whether the out-of-bounds read can cause denial of service or information exposure.

Mitigation direction

  • Check kernel vendor advisories for CVE-2023-53726 coverage.
  • Update to a kernel build containing the listed stable fixes.
  • Prioritize arm64 systems with exposed or high-throughput networking paths.
  • Track distro backports because version strings alone may be misleading.

Validation and detection

  • Inventory arm64 Linux kernels across servers, appliances, and images.
  • Map running kernel builds to vendor advisories or stable fix commits.
  • Confirm whether downstream kernels include the negative-length csum guard.
  • Review crash telemetry for related KASAN or checksum out-of-bounds reports.
Prepared
Confidence
medium
Sources
8

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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ATT&CK lookup starting points

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CVE-2023-53726 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
0ADP providers
7Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux5777eaed566a1d63e344d3dd8f2b5e33be20643e, 5777eaed566a1d63e344d3dd8f2b5e33be20643e, 5777eaed566a1d63e344d3dd8f2b5e33be20643e, 5777eaed566a1d63e344d3dd8f2b5e33be20643e, 5777eaed566a1d63e344d3dd8f2b5e33be20643e, 5777eaed566a1d63e344d3dd8f2b5e33be20643eunaffected
LinuxLinux5.6, 0, 5.10.195, 5.15.132, 6.1.53, 6.4.16, 6.5.3, 6.6affected
Weakness

CWE details

No CWE listed

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