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Linux KernelOperating system · Linux

CVE-2008-2136

HIGH · 7.8 CVSS v2.0 Published 2008-05-16
Fix available
A fix is available. Upgrade to 2.4.36.5 / 2.6.25.3 or later.
See remediation →
87/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Memory leak in the ipip6_rcv function in net/ipv6/sit.c in the Linux kernel 2.4 before 2.4.36.5 and 2.6 before 2.6.25.3 allows remote attackers to cause a denial of service (memory consumption) via network traffic to a Simple Internet Transition (SIT) tunnel interface, related to the pskb_may_pull and kfree_skb functions, and management of an skb reference count.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Memory leak in the Linux kernel's IPv6 SIT (Simple Internet Transition) tunnel handling in the ipip6_rcv function in net/ipv6/sit.c. Improper management of skb (socket buffer) reference counts when using pskb_may_pull and kfree_skb causes memory to not be freed properly when processing network traffic to SIT tunnel interfaces, leading to memory exhaustion and denial of service.

MitigationUpgrade Linux kernel to version 2.4.36.5 or later for the 2.4 series, or 2.6.25.3 or later for the 2.6 series. Alternatively, apply the specific patch addressing the skb reference count issue in the ipip6_rcv function.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 2.4.0, < 2.4.36.5>= 2.6.0, < 2.6.25.3
Debian LinuxOperating system
Affected:= 4.0
Ubuntu LinuxOperating system
Affected:= 6.06= 7.04= 7.10= 8.04

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Authentication
None
Confidentiality
None
Integrity
None
Availability
Complete

AV:N/AC:L/Au:N/C:N/I:N/A:C

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check the running kernel version
    Run 'uname -r' to display the currently running kernel version
    Affected if The version is less than 2.4.36.5 for 2.4 series, or less than 2.6.25.3 for 2.6 series (including 2.6.x versions before 2.6.25.3)
  2. Verify if the SIT module is loaded
    Run 'lsmod | grep sit' or check /proc/modules for the sit module
    Affected if The SIT module is loaded (the vulnerability exists in the sit.ko module or compiled-in kernel code)
  3. Check for active SIT tunnel interfaces
    Run 'ip -6 tunnel show' or check 'ip link' for sit-type interfaces such as 'sit0'
    Affected if SIT tunnel interfaces exist (particularly sit0 or other manually configured SIT tunnels)
  4. Check if IPv6 is enabled
    Run 'cat /proc/net/if_inet6' or check if IPv6 is listed in 'ip -6 addr show'
    Affected if IPv6 is enabled (SIT tunneling is used for IPv6 over IPv4, so IPv6 must be active)
  5. Monitor for memory growth in skb allocations
    Check kernel memory usage over time using 'cat /proc/meminfo' or monitor 'Slab:' or 'SReclaimable:' values, or inspect 'dmesg' for kernel memory warnings
    Affected if Memory usage steadily increases without being freed, indicating the leak is being triggered by SIT traffic

You are affected if your kernel version is less than 2.4.36.5 or less than 2.6.25.3, and SIT tunneling (IPv6 over IPv4) is enabled and actively processing traffic.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Upgrade available Upgrade to 2.4.36.5 / 2.6.25.3 or later
Fixed in 2.4.36.52.6.25.3
Interim mitigation

Upgrade Linux kernel to version 2.4.36.5 or later for the 2.4 series, or 2.6.25.3 or later for the 2.6 series. Alternatively, apply the specific patch addressing the skb reference count issue in the ipip6_rcv function.

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing5.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,790
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Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2008-2136 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data