VulnerabilityPublished 10 Sep 2026

CVE-2026-88859: Red Hat Enterprise Linux 7 · Encoded URI Scheme XSS

Affects Red Hat Enterprise Linux 7Source CVE Database V5

Not known to be exploited · CVSS 6.3 Medium.

Data as of 26 Oct 2026, 10:12 UTC

CVSS 3.1 base score

6.3Medium

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

EPSS

0.5% chance of exploitation in 30 days – higher than 44% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-09-10.

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

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

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: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
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: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 10 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 26 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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, 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
Red Hat Enterprise Linux 6evolution	Affected–	Fixed in–
Red Hat Enterprise Linux 7evolution	Affected–	Fixed in–
Red Hat Enterprise Linux 8evolution	Affected–	Fixed in–
Red Hat Enterprise Linux 9evolution	Affected–	Fixed in–

AI-suggested

Users should disable JavaScript execution for HTML mail in Evolution to mitigate this vulnerability. This can be done via Evolution preferences or by running the command `gsettings set org.gnome.evolution.mail enable-javascript false`. Disabling JavaScript may reduce functionality or rendering quality of some legitimate HTML emails. To revert, run `gsettings set org.gnome.evolution.mail enable-javascript true`. A restart of Evolution may be required for the setting to take full effect.

Description

CVE-2026-88859 is a vulnerability in Evolution on Red Hat Enterprise Linux 7 where a specially crafted HTML email with a spoofed vCard control can cause arbitrary JavaScript execution. This occurs because Evolution's trusted JavaScript handler incorrectly assigns an attacker-controlled JavaScript URL to an iframe's source, bypassing script execution restrictions in email content. The vulnerability requires user interaction (clicking the control) and has a medium severity rating with a CVSS score of 6.3. Mitigation involves disabling JavaScript execution in HTML emails within Evolution.

Impact

An attacker can execute arbitrary JavaScript code in the context of the mail viewer in Evolution, potentially leading to information disclosure, integrity loss, or availability impact within the user's mail session. The attack requires the victim to click on a specially crafted control in an email. The impact is limited to the mail-viewing context and does not require privileges or elevated access.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 08:28 UTC

Technical details

References

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