CVE-2024-26752 l2tp: pass correct message length to ip6_append_data

2024-04-0317:00:37

Linux

www.cve.org

l2tp

message length

ip6_append_data

linux kernel

vulnerability

calculation

c operator precedence

corrupted packets

7.8 High

AI Score

Confidence

High

0.0004 Low

EPSS

Percentile

13.2%

JSON

In the Linux kernel, the following vulnerability has been resolved:

l2tp: pass correct message length to ip6_append_data

l2tp_ip6_sendmsg needs to avoid accounting for the transport header
twice when splicing more data into an already partially-occupied skbuff.

To manage this, we check whether the skbuff contains data using
skb_queue_empty when deciding how much data to append using
ip6_append_data.

However, the code which performed the calculation was incorrect:

 ulen = len + skb_queue_empty(&sk-&gt;sk_write_queue) ? transhdrlen : 0;

…due to C operator precedence, this ends up setting ulen to
transhdrlen for messages with a non-zero length, which results in
corrupted packets on the wire.

Add parentheses to correct the calculation in line with the original
intent.

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "net/l2tp/l2tp_ip6.c"
    ],
    "versions": [
      {
        "version": "559d697c5d07",
        "lessThan": "4c3ce64bc9d3",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "1fc793d68d50",
        "lessThan": "c1d3a84a67db",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "96b2e1090397",
        "lessThan": "dcb4d1426859",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "cd1189956393",
        "lessThan": "0da15a703951",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "f6a7182179c0",
        "lessThan": "13cd1daeea84",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "9d4c75800f61",
        "lessThan": "804bd8650a3a",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "9d4c75800f61",
        "lessThan": "83340c66b498",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "9d4c75800f61",
        "lessThan": "359e54a93ab4",
        "status": "affected",
        "versionType": "git"
      }
    ]
  },
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "affected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "net/l2tp/l2tp_ip6.c"
    ],
    "versions": [
      {
        "version": "6.6",
        "status": "affected"
      },
      {
        "version": "0",
        "lessThan": "6.6",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "4.19.308",
        "lessThanOrEqual": "4.19.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.4.270",
        "lessThanOrEqual": "5.4.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.10.211",
        "lessThanOrEqual": "5.10.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.15.150",
        "lessThanOrEqual": "5.15.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.1.80",
        "lessThanOrEqual": "6.1.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.6.19",
        "lessThanOrEqual": "6.6.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.7.7",
        "lessThanOrEqual": "6.7.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.8",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]