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CVE Record

CVE-2025-71128: erspan: Initialize options_len before referencing options.

In the Linux kernel, the following vulnerability has been resolved: erspan: Initialize options_len before referencing options. The struct ip_tunnel_info has a flexible array member named options that is protected by a counted_by(options_len) attribute. The compiler will use this information to enforce runtime bounds checking deployed by FORTIFY_SOURCE string helpers. As laid out in the GCC documentation, the counter must be initialized before the first reference to the flexible array member. After scanning through the files that use struct ip_tunnel_info and also refer to options or options_len, it appears the normal case is to use the ip_tunnel_info_opts_set() helper. Said helper would initialize options_len properly before copying data into options, however in the GRE ERSPAN code a partial update is done, preventing the use of the helper function. Before this change the handling of ERSPAN traffic in GRE tunnels would cause a kernel panic when the kernel is compiled with GCC 15+ and having FORTIFY_SOURCE configured: memcpy: detected buffer overflow: 4 byte write of buffer size 0 Call Trace: <IRQ> __fortify_panic+0xd/0xf erspan_rcv.cold+0x68/0x83 ? ip_route_input_slow+0x816/0x9d0 gre_rcv+0x1b2/0x1c0 gre_rcv+0x8e/0x100 ? raw_v4_input+0x2a0/0x2b0 ip_protocol_deliver_rcu+0x1ea/0x210 ip_local_deliver_finish+0x86/0x110 ip_local_deliver+0x65/0x110 ? ip_rcv_finish_core+0xd6/0x360 ip_rcv+0x186/0x1a0 Reported-at: https://launchpad.net/bugs/2129580

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A Linux kernel flaw can crash affected systems when they process ERSPAN traffic through GRE tunnels. The documented impact is loss of availability, not data theft or modification. Exposure depends on kernel version, ERSPAN/GRE use, and a build using GCC 15 or later with FORTIFY_SOURCE enabled.

Executive priority

Treat this as a high-priority availability issue for network monitoring, routing, and infrastructure hosts that process ERSPAN over GRE. Patch exposed systems promptly after vendor validation. Systems without that traffic path or documented build conditions warrant normal risk-based scheduling rather than emergency action.

Technical view

ERSPAN handling references the flexible options array in ip_tunnel_info before initializing its options_len counter. Runtime bounds checking then treats a four-byte copy as an overflow and invokes a FORTIFY panic. The supplied record describes a remotely reachable, unauthenticated kernel denial of service and references two stable-kernel fixes.

Likely exposure

Prioritize Linux systems that receive ERSPAN traffic over GRE and use kernels identified as affected in the CVE data. The demonstrated panic specifically requires GCC 15 or later with FORTIFY_SOURCE configured. Exact exposure for distribution kernels cannot be determined from the bundle because vendor backports and release mappings are not provided.

Exploitation context

The CVE is not listed as KEV, and the supplied sources provide no evidence of active exploitation. The documented failure is a kernel panic during ERSPAN packet handling. CVSS 3.1 scores it 7.5 with network reachability, low complexity, no privileges, no user interaction, and availability-only impact.

Researcher notes

The root issue is ordering: options_len must be initialized before the counted flexible-array member is referenced. The normal helper performs that ordering, but ERSPAN uses a partial update. The bundle identifies fix commits but does not establish affected distribution packages, backport status, or exploitation in the wild.

Mitigation direction

  • Apply a vendor-supported kernel containing the referenced stable fix.
  • Check distribution guidance for fixed package versions and backports.
  • Restrict untrusted ERSPAN or GRE traffic where operationally feasible.
  • Prioritize externally reachable or shared infrastructure that processes ERSPAN traffic.

Validation and detection

  • Inventory kernel versions on systems using GRE or ERSPAN.
  • Identify builds using GCC 15 or later with FORTIFY_SOURCE enabled.
  • Confirm vendor packages include one of the referenced fixes or an equivalent backport.
  • Review kernel logs for FORTIFY panics associated with erspan_rcv.
  • Retest ERSPAN processing safely after patching in a controlled environment.
Prepared
Confidence
high
Sources
5

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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CVE-2025-71128 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

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

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.

1CVSS vectors
3Timeline events
0ADP providers
3Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2025-71128Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

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
LinuxLinuxbb5e62f2d547c4de6d1b144cbce2373a76c33f18, bb5e62f2d547c4de6d1b144cbce2373a76c33f18unaffected
LinuxLinux6.15, 0, 6.18.4, 6.19affected
Weakness

CWE details

No CWE listed

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