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CVE-2026-128238 Scapy before 2.8.0 Uncontrolled Recursion DoS via BER SEQUENCE Decoder

6.9 mediumEPSS 0.5%

Medium (6.9) in secdev scapy. EPSS 0.5% estimated probability of exploitation activity in the next 30 days.

On this page
Scapy before 2.8.0 contains an uncontrolled recursion vulnerability in the BER/ASN.1 decoder in scapy/asn1/ber.py that allows unauthenticated remote attackers to crash parsing applications. Attackers can send a single 833-byte packet with 250 nested ASN.1 SEQUENCE structures to trigger an unhandled RecursionError, terminating TLS, SNMP, X.509, or LDAP parsers even with safe=True.

Severity

CVSS 4.0

6.9 medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

CVSS 3.1

5.3 medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
EPSS
0.5% estimated probability of exploitation activity in the next 30 days; 45th percentile. Scored 2026-11-13. A forecast for this CVE across the internet, not for your own systems.
CISA's assessment (SSVC)
Exploitation: none · Automatable: yes · Technical impact: partial, assessed 2026-11-13. From CISA's Vulnrichment in the CVE List: whether it is exploited, whether exploiting it can be automated, and how much control it gives.
CWE
CWE-674 Uncontrolled Recursion
Published
Modified
Assigned by
VulnCheck (CNA)
NVD analysis
Awaiting analysis
Record from
the NVD, synced

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Affected

Versions

From the CNA's record in the CVE List.

ProductAffected
secdev scapybefore 2.8.0

Linux distributions

DistributionReleasePackageFixed inAdvisory
Ubuntu16.04:LTS, 18.04:LTS, 20.04:LTS and 4 morescapyno fix listedUBUNTU-CVE-2026-128238

From the distributions' data via OSV.dev: Ubuntu Security Notices © Canonical Ltd., CC BY-SA 4.0. Modified: reformatted and linked to CVE records. Credits. On the distributions' own pages: Ubuntu.

Attack patterns (CAPEC)

  • CAPEC-230 Serialized Data with Nested Payloads Likelihood: Medium · Severity: High
  • CAPEC-231 Oversized Serialized Data Payloads Likelihood: Medium · Severity: High

The attack patterns MITRE's CAPEC relates to this record's weaknesses, as MITRE names them. Credits.

References

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