VulnerabilityPublished 13 Aug 2026Updated 31 Oct 2026

CVE-2026-59886: pyasn1 · Uncontrolled resource consumption when converting decoded REAL values

Affects parsedmarcSource GCVE Database

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Not known to be exploited · CVSS 7.5 High : upgrade to 10.2.1 soon.

Data as of 1 Nov 2026, 00:22 UTC

CVSS 3.1 base score

7.5High

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

Patch: Available – fixed in 10.2.1

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 13 Aug 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 31 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

Upgrade parsedmarc to 10.2.1.

Affected software

Product	Affected	Fixed in
Homebrewparsedmarc`pkg:brew/parsedmarc`Other threats	Affected >=8.11.0 <10.2.1	Fixed in 10.2.1

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

AI-suggested

A patch is available and the issue is fixed in pyasn1 version 10.2.1. Users should upgrade to this version or later. As a workaround, avoid converting, printing, or comparing decoded Real objects from untrusted sources; instead, inspect the raw (mantissa, base, exponent) tuple. No other mitigations are required.

Description

CVE-2026-59886 is a denial-of-service vulnerability in the pyasn1 library's handling of ASN.1 REAL values. The issue arises when converting decoded REAL values with very large exponents to Python floats, causing excessive CPU and memory consumption that can hang the process. This affects pyasn1 versions from 8.11.0 up to but not including 10.2.1. The vulnerability is triggered by operations such as printing, logging, or comparing decoded REAL objects from untrusted ASN.1 data. It does not occur during decoding alone. The issue is fixed in pyasn1 version 10.2.1.

Impact

This vulnerability allows an attacker to cause a denial of service by supplying specially crafted ASN.1 REAL values with large exponents to applications using vulnerable pyasn1 versions. The excessive CPU and memory consumption occurs when the application converts, prints, logs, or compares these decoded REAL values, potentially hanging the process. There is no impact on confidentiality or integrity, and decoding alone does not trigger the issue.

Summary

The pyasn1 library's univ.Real type converts its (mantissa, base, exponent) tuple to a Python float using exact big-integer exponentiation. When decoding BER/CER/DER-encoded REAL values with large exponents, this conversion attempts to create an astronomically large integer, leading to uncontrolled resource consumption. Any operation that triggers float conversion on such a value—such as prettyPrint(), str(), comparisons, arithmetic, or explicit float() calls—results in excessive CPU and memory use, causing the process to hang. The vulnerability affects pyasn1.type.univ.Real and is reachable through pyasn1 codec decoders for BER, CER, and DER. The issue is fixed in pyasn1 version 10.2.1 by changing the conversion method to use math.ldexp() for binary values and raising OverflowError for decimal values with out-of-range exponents, preventing large intermediate integer construction.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 1 Nov 2026, 00:22 UTC

Technical details

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